Substrate holding apparatus and polishing apparatus

ABSTRACT

The present invention relates to a substrate holding apparatus for holding a substrate such as a semiconductor wafer in a polishing apparatus for polishing the substrate to a flat finish. The substrate holding apparatus according to the present invention comprises a top ring body having a receiving space therein, and a vertically movable member which is vertically movable within the receiving space in the top ring body. An abutment member having an elastic membrane is attached to a lower surface of the vertically movable member. The elastic membrane of the abutment member comprises an abutment portion, having a flange projecting outwardly, brought into direct or indirect contact with the substrate, and a connecting portion extending upwardly from a base portion of the flange of the abutment portion and being connected to the vertically movable member. The connecting portion is made of a material having a flexibility higher than that of material of the abutment portion.

This application is a National Stage application of PCT/JP02/12816,filed Dec. 6, 2002.

TECHNICAL FIELD

The present invention relates to a substrate holding apparatus forholding a substrate to be polished and pressing the substrate against apolishing surface, and more particularly to a substrate holdingapparatus for holding a substrate such as a semiconductor wafer in apolishing apparatus for polishing the substrate to a flat finish. Thepresent invention also relates to a polishing apparatus having such asubstrate holding apparatus.

BACKGROUND ART

In recent years, semiconductor devices have become more integrated, andstructures of semiconductor elements have become more complicated.Further, a number of layers in multilayer interconnections used for alogical system has been increased. Accordingly, irregularities on asurface of a semiconductor device become increased, so that step heightson the surface of the semiconductor device tend to be larger. This isbecause, in a manufacturing process of a semiconductor device, a thinfilm is formed on a semiconductor device, then micromachining processes,such as patterning or forming holes, are performed on the semiconductordevice, and these processes are repeated many times to form subsequentthin films on the semiconductor device.

When a number of irregularities is increased on a surface of asemiconductor device, the following problems arise. A thickness of afilm formed in a portion having a step is relatively small when a thinfilm is formed on a semiconductor device. An open circuit is caused bydisconnection of interconnections, or a short circuit is caused byinsufficient insulation between interconnection layers. As a result,good products cannot be obtained, and yield tends to be reduced.Further, even if a semiconductor device initially works normally,reliability of the semiconductor device is lowered after long-term use.At a time of exposure during a lithography process, if an irradiationsurface has irregularities, then a lens unit in an exposure system islocally unfocused. Therefore, if the irregularities of the surface ofthe semiconductor device are increased, then this becomes problematic inthat it is difficult to form a fine pattern itself on the semiconductordevice.

Accordingly, in a manufacturing process of a semiconductor device, itincreasingly becomes important to planarize a surface of thesemiconductor device. The most important one of planarizing technologiesis CMP (Chemical Mechanical Polishing). In such chemical mechanicalpolishing, with use of a polishing apparatus, while a polishing liquidcontaining abrasive particles such as silica (SiO2) therein is suppliedonto a polishing surface such as a polishing pad, a substrate such as asemiconductor wafer is brought into sliding contact with the polishingsurface, so that the substrate is polished.

This type of polishing apparatus comprises a polishing table having apolishing surface constituted by a polishing pad, and a substrateholding apparatus, which is called as a top ring or a carrier head, forholding a semiconductor wafer. When a semiconductor wafer is polishedwith such a polishing apparatus, the semiconductor wafer is held andpressed against the polishing table under a predetermined pressure bythe substrate holding apparatus. At this time, the polishing table andthe substrate holding apparatus are moved relatively to each other tobring the semiconductor wafer into sliding contact with the polishingsurface, so that a surface of the semiconductor wafer is polished to aflat mirror finish.

In such a polishing apparatus, if a relative pressing force between thesemiconductor wafer being polished and the polishing surface of thepolishing pad is not uniform over an entire surface of the semiconductorwafer, then the semiconductor wafer may insufficiently be polished ormay excessively be polished at some portions depending on a pressingforce applied to those portions of the semiconductor wafer. Therefore,it has been attempted to form a surface, for holding a semiconductorwafer, of a substrate holding apparatus by an elastic membrane made ofan elastic material such as rubber and to supply fluid pressure such asair pressure to a backside surface of the elastic membrane to uniformizepressing forces applied to the semiconductor wafer over an entiresurface of the semiconductor wafer.

Further, the polishing pad is so elastic that pressing forces applied toa peripheral portion of the semiconductor wafer being polished becomenon-uniform, and hence only the peripheral portion of the semiconductorwafer may excessively be polished, which is referred to as “edgerounding”. In order to prevent such edge rounding, there has been used asubstrate holding apparatus in which a semiconductor wafer is held atits peripheral portion by a guide ring or a retainer ring, and anannular portion of the polishing surface that corresponds to theperipheral portion of the semiconductor wafer is pressed by the guidering or retainer ring.

A thickness of a thin film formed on a surface of a semiconductor wafervaries from position to position in a radial direction of thesemiconductor wafer depending on a film deposition method orcharacteristics of a film deposition apparatus. Specifically, the thinfilm has a film thickness distribution in the radial direction of thesemiconductor wafer. Since a conventional substrate holding apparatus,as described above, for uniformly pressing an entire surface of asemiconductor wafer polishes the semiconductor wafer uniformly over theentire surface thereof, it cannot realize a polishing amountdistribution that is equal to the aforementioned film thicknessdistribution on the surface of the semiconductor wafer. Therefore, theconventional polishing apparatus cannot sufficiently cope with the filmthickness distribution in the radial direction, and insufficient orexcessive polishing is caused.

Further, the aforementioned film thickness distribution on the surfaceof the semiconductor wafer varies depending on a type of a filmdeposition method or a film deposition apparatus. Specifically,positions and a number of portions having a large film thickness in aradial direction and differences in thickness between thin film portionsand thick film portions vary depending on the type of a film depositionmethod or the film deposition apparatus. Therefore, a substrate holdingapparatus capable of easily coping with various film thicknessdistributions at low cost has been required rather than a substrateholding apparatus capable of coping with only a specific film thicknessdistribution.

In a substrate holding apparatus having a structure for pressing aportion of a polishing surface that corresponds to a peripheral portionof a semiconductor wafer by a guide ring or retainer ring in order toprevent edge rounding, non-uniform polishing such as edge roundingcannot sufficiently be suppressed in some cases by merely controllingpressing forces of the aforementioned guide ring or retainer ring.Generally, no devices are formed on a peripheral portion of asemiconductor wafer. Nevertheless, for a purpose of preventing elutionof metal or other defects, it is required that a polishing rate isintentionally reduced at a peripheral portion of a semiconductor waferso that an underlayer film is not exposed, or, on the contrary, apolishing rate is intentionally increased at a peripheral portion of asemiconductor wafer so as to remove a film on the peripheral portion ofthe semiconductor wafer. A conventional polishing apparatus cannotsufficiently control a polishing rate at a peripheral portion of asemiconductor wafer to a desired level.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above prior art. Itis, therefore, a first object of the present invention to provide asubstrate holding apparatus and a polishing apparatus which can polish athin film, formed on a surface of a workpiece such as a semiconductorwafer, having a film thickness distribution, and can obtain a uniformfilm thickness after polishing.

Further, the present invention has been made in view of the above priorart in which a polishing rate at a peripheral portion of a workpiececannot sufficiently be controlled to a desired level. It is, therefore,a second object of the present invention to provide a substrate holdingapparatus and a polishing apparatus which can uniformly polish aworkpiece such as a semiconductor wafer while controlling a polishingrate at a peripheral portion of the workpiece to a desired level.

In order to attain the first object, according to a first aspect of thepresent invention, there is provided a substrate holding apparatus forholding and pressing a substrate to be polished against a polishingsurface, characterized in that: the substrate holding apparatuscomprises a top ring body having a receiving space therein, and avertically movable member which is vertically movable within thereceiving space in the top ring body; an abutment member having anelastic membrane is attached to a lower surface of the verticallymovable member; the elastic membrane of the abutment member comprises anabutment portion, having flanges projecting outwardly and inwardly,brought into direct or indirect contact with the substrate, andconnecting portion extending upwardly from base portions of the flangesof the abutment portion and being connected to the vertically movablemember; and the connecting portions are made of a material having aflexibility higher than that of material of the abutment portion.

With this arrangement, pressures to be applied to the substrate canindependently be controlled, and hence a pressing force applied to athicker area of a thin film can be made higher than a pressing forceapplied to a thinner area of the thin film, thereby selectivelyincreasing a polishing rate of the thicker area of the thin film. Thus,an entire surface of a substrate can be polished exactly to a desiredlevel irrespective of a film thickness distribution obtained at a timethe thin film is formed. Further, even if the vertically movable memberis pressed downwardly for polishing, excessive downward forces are notapplied to the substrate which is brought into close contact with theabutment portion because the connecting portion is elastically deformed,so that a uniform polishing rate can be achieved in an area between thebase portions of the flanges. Further, even if the vertically movablemember is lifted for polishing, excessive upward forces are not appliedto the abutment portion because the connecting portion is likely toextend, so that a vacuum is not formed near the base portions of theflanges to achieve a uniform polishing rate in an area between the baseportions.

According to a second aspect of the present invention, there is provideda substrate holding apparatus for holding and pressing a substrate to bepolished against a polishing surface, characterized in that: thesubstrate holding apparatus comprises a top ring body having a receivingspace therein, and a vertically movable member which is verticallymovable within the receiving space in the top ring body; an abutmentmember having an elastic membrane is attached to a lower surface of thevertically movable member; the elastic membrane of the abutment membercomprises an abutment portion, having flanges projecting outwardly andinwardly, brought into direct or indirect contact with the substrate,and connecting portions extending upwardly from base portions of theflanges of the abutment portion and being connected to the verticallymovable member; and the connecting portions comprise a thin portionhaving a thickness smaller than that of the abutment portion.

With this arrangement, an entire surface of a substrate can be polishedexactly to a desired level irrespective of a film thickness distributionobtained at a time the thin film is formed. Simultaneously, even if thevertically movable member is pressed downwardly for polishing, excessivedownward forces are not applied to the substrate which is brought intoclose contact with the abutment portion because the connecting portionis likely to be deformed at the thin portion, so that a uniformpolishing rate can be achieved in an area between the base portions ofthe flanges. Further, even if the vertically movable member is liftedfor polishing, excessive upward forces are not applied to the abutmentportion because the thin portions are likely to extend, so that a vacuumis not formed near the base portions of the flanges to achieve a uniformpolishing rate in an area between the base portions. Particularly, whenthe thin portions are formed so as to be constricted inwardly incross-section, these effects can effectively be achieved.

According to a third aspect of the present invention, there is provideda substrate holding apparatus for holding and pressing a substrate to bepolished against a polishing surface, characterized in that: thesubstrate holding apparatus comprises a top ring body having a receivingspace therein, and a vertically movable member which is verticallymovable within the receiving space in the top ring body; an abutmentmember having an elastic membrane is attached to a lower surface of thevertically movable member; the elastic membrane of the abutment membercomprises an abutment portion, having flanges projecting outwardly andinwardly, brought into direct or indirect contact with the substrate,and connecting portions extending upwardly from base portions of theflanges of the abutment portion and being connected to the verticallymovable member; and adhesiveness of a lower surface of the base portionsof the flanges of the abutment portion is weakened.

With this arrangement, an entire surface of a substrate can be polishedexactly to a desired level irrespective of a film thickness distributionobtained at a time a thin film is formed. Simultaneously, even if thevertically movable member is lifted for polishing, a vacuum is unlikelyto be formed near the base portions of the flanges because the baseportions of the flanges is unlikely to be brought into close contactwith the substrate. Therefore, a uniform polishing rate can be achievedin an area between base portions.

In this case, an intermediate member having a low adhesiveness to thesubstrate may be disposed on a lower surface of the base portions of theflanges of the abutment portion to weaken adhesiveness of the lowersurface of the base portions of the flanges. Alternatively, adhesivenessbetween the base portions of the flanges and the substrate may beweakened by, for example, forming a groove in the lower surface of thebase portions of the flanges, or by forming the lower surface of thebase portions as a rough surface.

According to a fourth aspect of the present invention, there is provideda substrate holding apparatus for holding and pressing a substrate to bepolished against a polishing surface, characterized in that: thesubstrate holding apparatus comprises a top ring body having a receivingspace therein, and a vertically movable member which is verticallymovable within the receiving space in the top ring body; an abutmentmember having an elastic membrane is attached to a lower surface of thevertically movable member; the elastic membrane of the abutment membercomprises an abutment portion, having flanges projecting outwardly andinwardly, brought into direct or indirect contact with the substrate,and connecting portions extending upwardly from base portions of theflanges of the abutment portion and being connected to the verticallymovable member; and a hard member made of a material harder than that ofthe elastic membrane is embedded in the base portions of the flanges ofthe abutment portion. In this case, the hard member should preferablyhave an annular shape.

With this arrangement, an entire surface of a substrate can be polishedexactly to a desired level irrespective of a film thickness distributionobtained at a time the thin film is formed. Simultaneously, even if thevertically movable member is downwardly pressed for polishing, excessivedownward forces are not applied to the substrate which is brought intoclose contact with the abutment portion because downward forces by theconnecting portions are dispersed by the hard members, so that a uniformpolishing rate can be achieved in an area between base portions of theflanges. Further, even if the vertically movable member is lifted forpolishing, a vacuum is not formed near the base portions of the flangesbecause the hard member prevents deformation of the vicinity of the baseportions of the flanges. Therefore, a uniform polishing rate can beachieved in an area between the base portions of the flanges.

According to a fifth aspect of the present invention, there is provideda substrate holding apparatus for holding and pressing a substrate to bepolished against a polishing surface, characterized in that: thesubstrate holding apparatus comprises a top ring body having a receivingspace therein, and a vertically movable member which is verticallymovable within the receiving space in the top ring body; an abutmentmember having an elastic membrane is attached to a lower surface of thevertically movable member; and the elastic membrane of the abutmentmember comprises an abutment portion, having flanges projectingoutwardly and inwardly, brought into direct or indirect contact with thesubstrate, an extending portion extending outwardly from a base portionof each flange to a position inward of a tip of this flange to form agroove between the extending portion and the flange of the abutmentportion, and a connecting portion extending upwardly from an outward endof the extending portion and being connected to the vertically movablemember.

With this arrangement, an entire surface of a substrate can be polishedexactly to a desired level irrespective of a film thickness distributionobtained at a time a thin film is formed. Further, in a case where thevertically movable member is lifted for polishing after the substrate isbrought into close contact with the abutment portion, upward forces bythe connecting portion are converted into forces in horizontal oroblique directions by the extending portion, and these converted forcesare applied to the base portions of the flanges. Therefore, upwardforces applied to the base portions of the flanges can be made extremelysmall, so that excessive upward forces are not applied to the abutmentportion. Accordingly, a vacuum is not formed near the base portions, sothat a uniform polishing rate can be achieved in an area between thebase portions.

According to a preferred aspect of the present invention, the connectingportion positioned radially inwardly and the connecting portionpositioned radially outwardly have different thicknesses. In this case,it is desirable that the connecting portion positioned radially inwardlyhas a thickness smaller than a thickness of the connecting portionpositioned radially outwardly.

According to a preferred aspect of the present invention, the flangeprojecting radially outwardly and the flange projecting radiallyinwardly have different lengths. In this case, it is desirable that theflange projecting radially outwardly has a length larger than that ofthe flange projecting radially inwardly.

Because a cylinder having a smaller curvature generally has a stiffnesslarger than a cylinder having a larger curvature, a vertical forceapplied to the base portion of the flange by the connecting portionpositioned radially inwardly becomes larger than a force applied to thebase portion of the flange by the connecting portion positioned radiallyoutwardly. Therefore, with the above arrangement, forces applied to thebase portions of the flange positioned radially inwardly and the flangepositioned radially outwardly can be adjusted to the same level, or asealing capability can be enhanced at the flange projecting radiallyoutwardly, so that a uniform polishing rate can be achieved in an areabetween the base portions.

According to a sixth aspect of the present invention, there is provideda substrate holding apparatus for holding and pressing a substrate to bepolished against a polishing surface, characterized in that: thesubstrate holding apparatus comprises a top ring body having a receivingspace therein, and a vertically movable member which is verticallymovable within the receiving space in the top ring body; an abutmentmember having an elastic membrane which is brought into direct orindirect contact with the substrate is attached to a lower surface ofthe vertically movable member; and the vertically movable member is madeof a material having a large stiffness.

With this arrangement, when the vertically movable member is made of amaterial having a large stiffness and a light weight, e.g., epoxy resin,the vertically movable member becomes unlikely to be bent, so thatpolishing rates are prevented from being locally increased. Further,when a material having no magnetism is selected as a material of thevertically movable member, a film thickness of a thin film formed on asurface of a semiconductor wafer to be polished can be measured with afilm thickness method using eddy current in such a state that thesemiconductor wafer is held.

According to a seventh aspect of the present invention, there isprovided a substrate holding apparatus for holding and pressing asubstrate to be polished against a polishing surface, characterized inthat: an abutment member having an elastic membrane is attached to alower surface of a top ring; the elastic membrane of the abutment membercomprises an abutment portion, having a flange projecting outwardly,brought into direct or indirect contact with the substrate, and aconnecting portion extending upwardly from a base portion of the flangeof the abutment portion and being connected to the top ring; and the topring has a support portion for supporting the flange of the abutmentmember.

With this arrangement, an entire surface of a substrate can be polishedexactly to a desired level irrespective of a film thickness distributionobtained at a time a thin film is formed. Simultaneously, when apressurized fluid is supplied into a space around the abutment member,the flange is prevented from being deformed and attached to a lowersurface of the top ring, thereby achieving stable polishing.

In this case, it is desirable that the support portion has a radiallength larger than a radial length of the flange of the abutment member.With such a support portion, the flange of the abutment member can besupported more reliably, so that more stable polishing can be achieved.

According to a preferred aspect of the present invention, a fluidintroduction groove for introducing a fluid into an upper surface of theflange of the abutment member is formed in the support portion. Withthis arrangement, since a pressurized fluid can be introduced into theupper surface of the flange, adhesiveness of the flange to the substratecan be enhanced to achieve stable polishing.

According to an eighth aspect of the present invention, there isprovided a substrate holding apparatus for holding and pressing asubstrate to be polished against a polishing surface, characterized inthat: the substrate holding apparatus comprises a top ring body having areceiving space therein, a vertically movable member which is verticallymovable within the receiving space in the top ring body, and a seal ringbeing brought into contact with an upper surface of a peripheral portionof the substrate; and the vertically movable member has a supportportion for supporting the seal ring, with the support portion having aradial length in a range of from 1 mm to 7 mm.

With this arrangement, an entire surface of a substrate can be polishedexactly to a desired level irrespective of a film thickness distributionobtained at a time a thin film is formed. Simultaneously, when apressurized fluid is supplied into a space around the seal ring, theseal ring is prevented from being deformed and attached to a lowersurface of the vertically movable member. Further, a peripheral portionof the substrate is likely to be excessively polished. However, when thesupport portion has a radial length in a range of from 1 mm to 7 mm, itis possible to prevent excessive polishing.

According to a preferred aspect of the present invention, a fluidintroduction groove for introducing a fluid into an upper surface of theseal ring is formed in the support portion of the vertically movablemember. With this arrangement, since a pressurized fluid can beintroduced into the upper surface of the seal ring, adhesiveness of theseal ring to the substrate can be enhanced to achieve stable polishing.

In order to attain the second object, according to a ninth aspect of thepresent invention, there is provided a substrate holding apparatus forholding and pressing a substrate to be polished against a polishingsurface, characterized in that: the substrate holding apparatuscomprises a top ring body for holding the substrate, with an edge bagbeing brought into contact with a peripheral portion of the substrate,and a torque transmitting member being brought into contact with thesubstrate radially inwardly of the edge bag; and a pressure of a firstpressure chamber defined in the edge bag and a pressure of a secondpressure chamber defined radially inwardly of the edge bag areindependently controlled.

With this arrangement, sufficient torque can be transmitted to thesubstrate by the torque transmitting member. Further, an entire surfaceof the substrate except the peripheral portion thereof can be pressedagainst the polishing surface at a uniform force by pressure of thesecond pressure chamber, and pressure of the first pressure chamber canbe controlled independently of the pressure of the second pressurechamber. Therefore, it is possible to control a polishing rate at theperipheral portion of the substrate, i.e., a polishing profile of theperipheral portion of the substrate.

According to a preferred aspect of the present invention, the torquetransmitting member has a communication hole communicating a spaceinside of the torque transmitting member and a space outside of thetorque transmitting member with each other.

Further, in view of controlling a polishing rate of a peripheral portionof the semiconductor wafer, it is desirable that the edge bag definingthe first pressure chamber comprises a member having a radial width in arange of from 1 mm to 10 mm.

According to a preferred aspect of the present invention, the substrateholding apparatus comprises a retainer ring secured to or formedintegrally with the top ring body for holding a side edge portion of thesubstrate; and a pressing force to press the retainer ring against thepolishing surface is controlled independently of a pressure of thepressure chamber. In this manner, when the pressing force of theretainer ring is also controlled, more detailed control can be achieved.

A polishing apparatus according to the present invention comprises theaforementioned substrate holding apparatus and a polishing table havinga polishing surface.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view showing an entire arrangement of apolishing apparatus having a substrate holding apparatus according tothe present invention;

FIG. 2 is a vertical cross-sectional view showing a substrate holdingapparatus according to a first embodiment of the present invention;

FIG. 3 is a bottom view of the substrate holding apparatus shown in FIG.2;

FIG. 4 is a vertical cross-sectional view showing a first example of aring tube in the substrate holding apparatus according to the firstembodiment of the present invention;

FIG. 5 is a vertical cross-sectional view showing an elastic membrane ofthe ring tube shown in FIG. 4;

FIGS. 6A through 6C are vertical cross-sectional views showingdeformation of the elastic membrane of the ring tube;

FIG. 7 is a vertical cross-sectional view showing a second example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention;

FIG. 8 is a vertical cross-sectional view showing a third example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention;

FIG. 9 is a vertical cross-sectional view showing a fourth example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention;

FIG. 10 is a vertical cross-sectional view showing a fifth example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention;

FIG. 11 is a vertical cross-sectional view showing a sixth example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention;

FIGS. 12A through 12C are vertical cross-sectional views showing aseventh example of an elastic membrane of a ring tube in a substrateholding apparatus according to the present invention;

FIG. 13 is a vertical cross-sectional view showing a substrate holdingapparatus according to a second embodiment of the present invention;

FIG. 14 is a bottom view of the substrate holding apparatus shown inFIG. 13;

FIG. 15 is a vertical cross-sectional view showing a ring tube in thesubstrate holding apparatus according to the second embodiment of thepresent invention;

FIG. 16 is a vertical cross-sectional view showing a ring tube withoutany support portions in a chucking plate;

FIG. 17 is a partial perspective view showing a support portion of achucking plate of FIG. 15;

FIG. 18 is a vertical cross-sectional view showing a seal ring withoutany support portions in a chucking plate;

FIG. 19 is a vertical cross-sectional view showing a seal ring in thesubstrate holding apparatus of FIG. 15;

FIG. 20 is a vertical cross-sectional view showing a substrate holdingapparatus according to a third embodiment of the present invention;

FIG. 21 is a partial cross-sectional view showing an edge bag of FIG.20; and

FIG. 22 is a partial cross-sectional view showing a torque transmittingmember of FIG. 20.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A substrate holding apparatus and a polishing apparatus according toembodiments of the present invention will be described in detail belowwith reference to the drawings.

FIG. 1 is a cross-sectional view showing an entire arrangement of apolishing apparatus having a substrate holding apparatus according tothe present invention. The substrate holding apparatus serves to hold asubstrate such as a semiconductor wafer to be polished and to press thesubstrate against a polishing surface on a polishing table. As shown inFIG. 1, a polishing table 100 having a polishing pad 101 attached on anupper surface thereof is provided underneath a top ring 1 constituting asubstrate holding apparatus according to the present invention. Apolishing liquid supply nozzle 102 is provided above the polishing table100, and a polishing liquid Q is supplied onto the polishing pad 101 onthe polishing table 100 from the polishing liquid supply nozzle 102.

Various kinds of polishing pads are available on the market. Forexample, some of these are SUBA800, IC-1000, and IC-1000/SUBA400(two-layer cloth) manufactured by Rodel Inc., and Surfin xxx-5 andSurfin 000 manufactured by Fujimi Inc. SUBA800, Surfin xxx-5, and Surfin000 are non-woven fabrics bonded by urethane resin, and IC-1000 is madeof rigid foam polyurethane (single-layer). Foam polyurethane is porousand has a large number of fine recesses or holes formed in its surface.

The top ring 1 is connected to a top ring drive shaft 11 by a universaljoint 10, and the top ring drive shaft 11 is coupled to a top ring aircylinder 111 fixed to a top ring head 110. The top ring air cylinder 111operates to move the top ring drive shaft 11 vertically to thereby liftand lower the top ring 1 as a whole and to press a retainer ring 3 fixedto a lower end of a top ring body 2 against the polishing pad 101. Thetop ring air cylinder 111 is connected to a compressed air source 120via a regulator R1, which can regulate pressure of compressed air or thelike which is supplied to the top ring air cylinder 111. Thus, it ispossible to adjust a pressing force to press the polishing pad 101 withthe retainer ring 3.

The top ring drive shaft 11 is connected to a rotary sleeve 112 by a key(not shown). The rotary sleeve 112 has a timing pulley 113 fixedlydisposed at a peripheral portion thereof. A top ring motor 114 is fixedto the top ring head 110, and the timing pulley 113 is coupled to atiming pulley 116 mounted on the top ring motor 114 via a timing belt115. Therefore, when the top ring motor 114 is energized for rotation,the rotary sleeve 112 and the top ring drive shaft 11 are rotated inunison with each other via the timing pulley 116, the timing belt 115,and the timing pulley 113 to thereby rotate the top ring 1. The top ringhead 110 is supported on a top ring head shaft 117 fixedly supported ona frame (not shown).

Next, a substrate holding apparatus according to a first embodiment ofthe present invention will be described below. FIG. 2 is a verticalcross-sectional view showing top ring 1 of the substrate holdingapparatus according to the first embodiment, and FIG. 3 is a bottom viewof the top ring 1 shown in FIG. 2. As shown in FIG. 2, the top ring 1constituting a substrate holding apparatus comprises a top ring body 2in the form of a cylindrical housing with a receiving space definedtherein, and a retainer ring 3 fixed to a lower end of the top ring body2. The top ring body 2 is made of a material having high strength andrigidity, such as metal or ceramic. The retainer ring 3 is made ofhighly rigid synthetic resin, ceramic, or the like.

The top ring body 2 comprises a cylindrical housing 2 a, an annularpressurizing sheet support 2 b fitted into a cylindrical portion of thehousing 2 a, and an annular seal 2 c fitted over an outercircumferential edge of an upper surface of the housing 2 a. Theretainer ring 3 is fixed to the lower end of the housing 2 a of the topring body 2. The retainer ring 3 has a lower portion projecting radiallyinwardly. The retainer ring 3 may be formed integrally with the top ringbody 2.

Top ring drive shaft 11 is disposed above a central portion of thehousing 2 a of the top ring body 2, and the top ring body 2 is coupledto the top ring drive shaft 11 by universal joint 10. The universaljoint 10 has a spherical bearing mechanism by which the top ring body 2and the top ring drive shaft 11 are tillable with respect to each other,and a rotation transmitting mechanism for transmitting rotation of thetop ring drive shaft 11 to the top ring body 2. The spherical bearingmechanism and the rotation transmitting mechanism transmit a pressingforce and a rotating force from the top ring drive shaft 11 to the topring body 2 while allowing the top ring body 2 and the top ring driveshaft 11 to be tilted with respect to each other.

The spherical bearing mechanism comprises a hemispherical concave recess11 a defined centrally in a lower surface of the top ring drive shaft11, a hemispherical concave recess 2 d defined centrally in an uppersurface of the housing 2 a, and a ball bearing 212 made of a highly hardmaterial such as ceramic and interposed between the concave recesses 11a and 2 d. On the other hand, the rotation transmitting mechanismcomprises drive pins (not shown) fixed to the top ring drive shaft 11,and driven pins (not shown) fixed to the housing 2 a. Even if the topring body 2 is tilted with respect to the top ring drive shaft 11, thedrive pins and the driven pins remain in engagement with each otherwhile contact points are displaced because the drive pins and the drivenpins are vertically movable relatively to each other. Thus, the rotationtransmitting mechanism reliably transmits rotational torque of the topring drive shaft 11 to the top ring body 2.

The top ring body 2 and the retainer ring 3 secured to the top ring body2 have a space defined therein, which accommodates therein a seal ring204 having a lower surface brought into contact with a peripheralportion of a semiconductor wafer W held by the top ring 1, an annularholder ring 205, and a disk-shaped chucking plate 206 (verticallymovable member) which is vertically movable within the receiving spacein the top ring body 2. The seal ring 204 has a radially outer edgeclamped between the holder ring 205 and the chucking plate 206 securedto a lower end of the holder ring 205 and extends radially inwardly soas to cover a lower surface of the chucking plate 206 near its outercircumferential edge. A lower end surface of the seal ring 204 isbrought into contact with an upper surface of the semiconductor wafer Wto be polished. The semiconductor wafer W has a recess defined in anouter edge thereof, which is referred to as a notch or orientation flat,for recognizing (identifying) an orientation of the semiconductor wafer.The seal ring 204 should preferably extend radially inwardly of thechucking plate 206 from an innermost position of such notch ororientation flat.

The chucking plate 206 may be made of metal. However, when a thicknessof a thin film formed on a surface of a semiconductor wafer is measuredby a method using eddy current in a state such that this semiconductorwafer to be polished is held by the top ring, the chucking plate 206should preferably be made of a non-magnetic material, e.g., aninsulating material such as fluororesin, epoxy resin, or ceramic.

A pressurizing sheet 207 comprising an elastic membrane extends betweenthe holder ring 205 and the top ring body 2. The pressurizing sheet 207has a radially outer edge clamped between the housing 2 a and thepressurizing sheet support 2 b of the top ring body 2, and a radiallyinner edge clamped between an upper end portion 205 a and a stopper 205b of the holder ring 205. The top ring body 2, the chucking plate 206,the holder ring 205, and the pressurizing sheet 207 jointly define apressure chamber 221 in the top ring body 2. As shown in FIG. 2, a fluidpassage 31 comprising tubes and connectors communicates with thepressure chamber 221, which is connected to compressed air source 120via a regulator R2 provided in the fluid passage 31. The pressurizingsheet 207 is made of a highly strong and durable rubber material such asethylene propylene rubber (EPDM), polyurethane rubber, or siliconerubber.

In a case where the pressurizing sheet 207 is made of an elasticmaterial such as rubber, if the pressurizing sheet 207 is fixedlyclamped between the retainer ring 3 and the top ring body 2, then adesired horizontal surface cannot be maintained on a lower surface ofthe retainer ring 3 because of elastic deformation of the pressurizingsheet 207 as an elastic material. In order to prevent such a drawback,the pressurizing sheet 207 is clamped between the housing 2 a of the topring body 2 and the pressurizing sheet support 2 b provided as aseparate member in the present embodiment. The retainer ring 3 mayvertically be movable with respect to the top ring body 2, or theretainer ring 3 may have a structure capable of pressing the polishingsurface independently of the top ring body 2. In such cases, thepressurizing sheet 207 is not necessarily fixed in the aforementionedmanner.

A cleaning liquid passage 251 in the form of an annular groove isdefined in an upper surface of the housing 2 a near its outercircumferential edge over which the seal 2 c of the top ring body 2 isfitted. The cleaning liquid passage 251 communicates with a fluidpassage 32 via a through-hole 252 formed in the seal 2 c, and issupplied with a cleaning liquid (pure water) via the fluid passage 32. Aplurality of communication holes 253 are defined in the housing 2 a andthe pressurizing sheet support 2 b in communication with the cleaningliquid passage 251. The communication holes 253 communicate with a smallgap G defined between an outer circumferential surface of the seal ring204 and an inner circumferential surface of the retainer ring 3.

A central bag 208 and a ring tube 209 which serve as abutment membersbrought into contact with the semiconductor wafer W are mounted in aspace defined between the chucking plate 206 and the semiconductor waferW. In the present embodiment, as shown in FIGS. 2 and 3, the central bag208 is disposed centrally on a lower surface of the chucking plate 206,and the ring tube 209 is disposed radially outwardly of the central bag208 in a surrounding relationship relative thereto. Each of the sealring 204, the central bag 208, and the ring tube 209 is made of a highlystrong and durable rubber material such as ethylene propylene rubber(EPDM), polyurethane rubber, or silicone rubber.

A space defined between the chucking plate 206 and the semiconductorwafer W is divided into a plurality of spaces by the central bag 208 andthe ring tube 209. Accordingly, a pressure chamber 222 is definedbetween the central bag 208 and the ring tube 209, and a pressurechamber 223 is defined radially outwardly of the ring tube 209.

The central bag 208 comprises an elastic membrane 281 brought intocontact with the upper surface of the semiconductor wafer W, and acentral bag holder 282 for detachably holding the elastic membrane 281in position. The central bag holder 282 has threaded holes 282 a definedtherein, and the central bag 208 is detachably fastened to a center ofthe lower surface of the chucking plate 206 by screws 255 threaded intothe threaded holes 282 a. The central bag 208 has a central pressurechamber 224 defined therein by the elastic membrane 281 and the centralbag holder 282.

Similarly, the ring tube 209 comprises an elastic membrane 291 broughtinto contact with the upper surface of the semiconductor wafer W, and aring tube holder 292 for detachably holding the elastic membrane 291 inposition. The ring tube holder 292 has threaded holes 292 a definedtherein, and the ring tube 209 is detachably fastened to the lowersurface of the chucking plate 206 by screws 256 threaded into thethreaded holes 292 a. The ring tube 209 has an intermediate pressurechamber 225 defined therein by the elastic membrane 291 and the ringtube holder 292.

In the present embodiment, the pressure chamber 224 is formed by theelastic membrane 281 of the central bag 208 and the central bag holder282, and the pressure chamber 225 is formed by the elastic membrane 291of the ring tube 209 and the ring tube holder 292. The pressure chambers222, 223 may also be formed by an elastic membrane and a holder forfixing the elastic membrane, respectively. Further, elastic membranesand holders may appropriately be added to increase a number of pressurechambers.

Fluid passages 33, 34, 35 and 36 comprising tubes and connectorscommunicate with the pressure chambers 222 and 223, the central pressurechamber 224, and the intermediate pressure chamber 225, respectively.The pressure chambers 222 to 225 are connected to the compressed airsource 120 as a supply source via respective regulators R3, R4, R5 andR6 connected respectively to the fluid passages 33 to 36. The fluidpassages 31 to 36 are connected to the respective regulators R1 to R6through a rotary joint (not shown) mounted on an upper end of the topring shaft 110.

The pressure chamber 221 above the chucking plate 206 and the pressurechambers 222 to 225 are supplied with pressurized fluids such aspressurized air or atmospheric air or evacuated, via the fluid passages31, 33, 34, 35 and 36 connected to respective pressure chambers. Asshown in FIG. 1, the regulators R2 to R6 connected to the fluid passages31, 33, 34, 35 and 36 of the pressure chambers 221 to 225 canrespectively regulate pressures of the pressurized fluids supplied tothe respective pressure chambers. Thus, it is possible to independentlycontrol the pressures in the pressure chambers 221 to 225 orindependently introduce atmospheric air or vacuum into the pressurechambers 221 to 225. In this manner, the pressures in the pressurechambers 221 to 225 are independently varied with the regulators R2 toR6, so that pressing forces to press the semiconductor wafer W againstthe polishing pad 101 can be adjusted in local areas of thesemiconductor wafer W. In some applications, the pressure chambers 221to 225 may be connected to a vacuum source 121.

In this case, the pressurized fluid or the atmospheric air supplied tothe pressure chambers 222 to 225 may independently be controlled interms of temperature. With this configuration, it is possible todirectly control a temperature of a workpiece such as a semiconductorwafer from a backside of a surface to be polished. Particularly, wheneach of the pressure chambers is independently controlled in terms oftemperature, a rate of chemical reaction can be controlled during achemical polishing process of CMP.

The chucking plate 206 has radially inner suction portions 261 extendeddownwardly therefrom between the central bag 208 and the ring tube 209.The chucking plate 206 has radially outer suction portions 262 extendeddownwardly therefrom outside of the ring tube 209. In the presentembodiment, eight suction portions 261, 262 are provided.

The inner suction portions 261 and the outer suction portions 262 havecommunication holes 261 a, 262 a communicating with fluid passages 37,38, respectively. The inner suction portions 261 and the outer suctionportions 262 are connected to the vacuum source 121 such as a vacuumpump via the fluid passages 37, 38 and valves V1, V2. When thecommunication holes 261 a, 262 a of the suction portions 261, 262 areconnected to the vacuum source 121, a negative pressure is developed atlower opening ends of the communication holes 261 a, 262 a thereof toattract a semiconductor wafer W to lower ends of the inner suctionportions 261 and the outer suction portions 262. The inner suctionportions 261 and the outer suction portions 262 have elastic sheets 261b, 262 b, such as thin rubber sheets, attached to their lower ends, forthereby elastically contacting and holding the semiconductor wafer W onlower surfaces thereof.

Since there is a small gap G between the outer circumferential surfaceof the seal ring 204 and the inner circumferential surface of theretainer ring 3, the holder ring 205, the chucking plate 206, and theseal ring 204 attached to the chucking plate 206 can vertically be movedwith respect to the top ring body 2 and the retainer ring 3, and henceare of a floating structure with respect to the top ring body 2 and theretainer ring 3. The stopper 205 b of the holder ring 205 has aplurality of teeth 205 c projecting radially outwardly from an outercircumferential edge thereof. Downward movement of members including theholder ring 205 is limited to a predetermined range by engaging theteeth 205 c with an upper surface of the radially inwardly projectingportion of the retainer ring 3.

Next, operation of the top ring 1 thus constructed will be described indetail below.

In the polishing apparatus constructed above, when a semiconductor waferW is to be delivered to the polishing apparatus, the top ring 1 as awhole is moved to a position to which the semiconductor wafer W istransferred, and the communication holes 261 a, 262 a of the innersuction portions 261 and the outer suction portions 262 are connectedvia the fluid passages 37, 38 to the vacuum source 121. Thesemiconductor wafer W is attracted under vacuum to the lower ends of theinner suction portions 261 and the outer suction portions 262 by suctioneffect of the communication holes 261 a, 262 a. With the semiconductorwafer W attracted to the top ring 1, the top ring 1 as a whole is movedto a position above the polishing table 100 having a polishing surface(polishing pad 101) thereon. An outer circumferential edge of thesemiconductor wafer W is held by the retainer ring 3 so that thesemiconductor wafer W is not removed from the top ring 1.

For polishing the semiconductor wafer W, attraction of semiconductorwafer W by the suction portions 261, 262 is released, and thesemiconductor wafer W is held on a lower surface of the top ring 1.Simultaneously, the top ring air cylinder 111 connected to the top ringdrive shaft 11 is actuated to press the retainer ring 3 fixed to a lowerend of the top ring 1 against the polishing surface on the polishingtable 100 under a predetermined pressure. In such a state, pressurizedfluids are respectively supplied to the pressure chambers 222, 223, thecentral pressure chamber 224, and the intermediate pressure chamber 225under respective pressures, thereby pressing the semiconductor wafer Wagainst the polishing surface on the polishing table 100. The polishingliquid supply nozzle 102 supplies a polishing liquid Q onto thepolishing pad 101 in advance, so that the polishing liquid Q is held onthe polishing pad 101. Thus, the semiconductor wafer W is polished bythe polishing pad 101 with the polishing liquid Q being present betweena (lower) surface, to be polished, of the semiconductor wafer W and thepolishing pad 101.

Local areas of the semiconductor wafer W that are positioned beneath thepressure chambers 222, 223 are pressed against the polishing surfaceunder pressures of the pressurized fluids supplied to the pressurechambers 222, 223. A local area of the semiconductor wafer W that ispositioned beneath the central pressure chamber 224 is pressed via theelastic membrane 281 of the central bag 208 against the polishingsurface under pressure of the pressurized fluid supplied to the centralpressure chamber 224. A local area of the semiconductor wafer W that ispositioned beneath the intermediate pressure chamber 225 is pressed viathe elastic membrane 291 of the ring tube 209 against the polishingsurface under pressure of the pressurized fluid supplied to theintermediate pressure chamber 225.

Therefore, polishing pressures acting on respective local areas of thesemiconductor wafer W can be adjusted independently by controllingpressures of the pressurized fluids supplied to the respective pressurechambers 222 to 225. Specifically, the respective regulators R3 to R6independently regulate the pressures of the pressurized fluids suppliedto the pressure chambers 222 to 225 for thereby adjusting pressingforces applied to press the local areas of the semiconductor wafer Wagainst the polishing pad 101 on the polishing table 100. With thepolishing pressures on the respective local areas of the semiconductorwafer W being adjusted independently to desired values, thesemiconductor wafer W is pressed against the polishing pad 101 on thepolishing table 100 that is being rotated. Similarly, pressure of thepressurized fluid supplied to the top ring air cylinder 111 can beregulated by the regulator R1 to adjust a force with which the retainerring 3 presses the polishing pad 101. While the semiconductor wafer W isbeing polished, the force with which the retainer ring 3 presses thepolishing pad 101 and the pressing force with which the semiconductorwafer W is pressed against the polishing pad 101 can appropriately beadjusted for thereby applying polishing pressures in a desired pressuredistribution to a central area (C1 in FIG. 3), an inner area (C2)between the central area and an intermediate area, the intermediate area(C3), a peripheral area (C4) of the semiconductor wafer W, and aperipheral portion of the retainer ring 3 which is positioned outside ofthe semiconductor wafer W.

In this manner, the semiconductor wafer W is divided into fourconcentric circular and annular areas (C1 to C4), which can respectivelybe pressed under independent pressing forces. A polishing rate dependson a pressing force applied to a semiconductor wafer W against apolishing surface. As described above, since the pressing forces appliedto those areas can independently be controlled, polishing rates of thefour circular and annular areas (C1 to C4) of the semiconductor wafer Wcan independently be controlled. Consequently, even if a thickness of athin film to be polished on the surface of the semiconductor wafer Wsuffers radial variations, the thin film on the surface of thesemiconductor wafer W can be polished uniformly without beinginsufficiently or excessively polished over an entire surface of thesemiconductor wafer. More specifically, even if the thickness of thethin film to be polished on the surface of the semiconductor wafer Wdiffers depending on a radial position of the semiconductor wafer W,pressure in a pressure chamber positioned over a thicker area of thethin film is made higher than pressure in other pressure chambers, orpressure in a pressure chamber positioned over a thinner area of thethin film is made lower than pressure in other pressure chambers. Inthis manner, a pressing force applied to the thicker area of the thinfilm against the polishing surface is made higher than a pressing forceapplied to the thinner area of the thin film against the polishingsurface, thereby selectively increasing a polishing rate of the thickerarea of the thin film. Consequently, the entire surface of thesemiconductor wafer W can be polished exactly to a desired level overthe entire surface of the semiconductor wafer W irrespective of a filmthickness distribution produced at a time the thin film is formed.

Any unwanted edge rounding on a circumferential edge of thesemiconductor wafer W can be prevented by controlling a pressing forceapplied to the retainer ring 3. If the thin film to be polished on thecircumferential edge of the semiconductor wafer W has large thicknessvariations, then the pressing force applied to the retainer ring 3 isintentionally increased or reduced to thus control a polishing rate ofthe circumferential edge of the semiconductor wafer W. When thepressurized fluids are supplied to the pressure chambers 222 to 225, thechucking plate 206 is subjected to upward forces. In the presentembodiment, pressurized fluid is supplied to the pressure chamber 221via the fluid passage 31 to prevent the chucking plate 206 from beinglifted under these forces due to the pressure chambers 222 to 225.

As described above, the pressing force applied by the top ring aircylinder 111 to press the retainer ring 3 against the polishing pad 101,and the pressing forces applied by the pressurized air supplied to thepressure chambers 222 to 225 to press the local areas of thesemiconductor wafer W against the polishing pad 101, are appropriatelyadjusted to polish the semiconductor wafer W. When polishing of thesemiconductor wafer W is finished, the semiconductor wafer W isattracted to the lower ends of the inner suction portions 261 and theouter suction portions 262 under vacuum in the same manner as describedabove. At this time, supply of the pressurized fluids into the pressurechambers 222 to 225 to press the semiconductor wafer W against thepolishing surface is stopped, and the pressure chambers 222 to 225 arevented to an atmosphere. Accordingly, the lower ends of the innersuction portions 261 and the outer suction portions 262 are brought intocontact with the semiconductor wafer W. The pressure chamber 221 isvented to the atmosphere or evacuated to develop a negative pressuretherein. If the pressure chamber 221 is maintained at a high pressure,then the semiconductor wafer W is strongly pressed against the polishingsurface only in areas brought into contact with the inner suctionportions 261 and the outer suction portions 262. Therefore, it isnecessary to decrease pressure in the pressure chamber 221 immediately.Accordingly, a relief port 239 penetrating from the pressure chamber 221through the top ring body 2 may be provided for decreasing the pressurein the pressure chamber 221 immediately, as shown in FIG. 2. In thiscase, when the pressure chamber 221 is pressurized, it is necessary tocontinuously supply pressurized fluid into the pressure chamber 221 viathe fluid passage 31. The relief port 239 comprises a check valve forpreventing an outside air from flowing into the pressure chamber 221 ata time when a negative pressure is developed in the pressure chamber221.

After attraction of the semiconductor wafer W, the top ring 1 as a wholeis moved to a position to which the semiconductor wafer W is to betransferred, and then a fluid (e.g., compressed air or a mixture ofnitrogen and pure water) is ejected to the semiconductor wafer W via thecommunication holes 261 a, 262 a of the inner suction portions 261 andthe outer suction portions 262 to release the semiconductor wafer W fromthe top ring 1.

The polishing liquid Q used to polish the semiconductor wafer W tends toflow through the small gap G between the outer circumferential surfaceof the seal ring 204 and the retainer ring 3. If the polishing liquid Qis firmly deposited in the gap G, then the holder ring 205, the chuckingplate 206, and the seal ring 204 are prevented from smoothly movingvertically with respect to the top ring body 2 and the retainer ring 3.To avoid such a drawback, a cleaning liquid (pure water) is suppliedthrough the fluid passage 32 to the cleaning liquid passage 251.Accordingly, the pure water is supplied via a plurality of communicationholes 253 to a region above the gap G, thus cleaning the gap G toprevent the polishing liquid Q from being firmly deposited in the gap G.The pure water should preferably be supplied after a polishedsemiconductor wafer W is released and until a next semiconductor waferto be polished is attracted to the top ring 1. It is also preferable todischarge all supplied pure water out of the top ring 1 before the nextsemiconductor wafer is polished, and hence to provide the retainer ring3 with a plurality of through-holes 3 a shown in FIG. 2. Furthermore, ifa pressure buildup is developed in a space 226 defined between theretainer ring 3, the holder ring 205, and the pressurizing sheet 207,then it acts to prevent the chucking plate 206 from being elevated inthe top ring body 2. Therefore, in order to allow the chucking plate 206to be elevated smoothly in the top ring body 2, the through-holes 3 ashould preferably be provided for equalizing pressure in the space 226with atmospheric pressure.

As described above, according to a substrate holding apparatus of thefirst embodiment, the pressures in the pressure chambers 222, 223,pressure chamber 224 in the central bag 208, and the pressure chamber225 in the ring tube 209 are independently controlled to controlpressing forces acting on the semiconductor wafer W.

A first example of the ring tube 209 in the substrate holding apparatusaccording to the first embodiment of the present invention will bedescribed in detail below. Although only the ring tube 209 will bedescribed below, the following description can be applied to the centralbag 208.

FIG. 4 is a vertical cross-sectional view showing the ring tube 209shown in FIG. 2, and FIG. 5 is a vertical cross-sectional view showingthe elastic membrane 291 of the ring tube 209 shown in FIG. 4. As shownin FIGS. 4 and 5, the elastic membrane 291 of the ring tube 209 in afirst example has an abutment portion 291 b having flanges 291 aprojecting outwardly and inwardly, and connecting portions 291 cconnected via the ring tube holder 292 to the chucking plate 206. Theconnecting portions 291 c extend upwardly from base portions 291 d ofthe flanges 291 a. A lower surface of the abutment portion 291 b isbrought into contact with the upper surface of the semiconductor waferW. The flanges 291 a, the abutment portion 291 b, and the connectingportions 291 c are integrally made of the same material.

As described above, when a semiconductor wafer is polished, pressurizedfluids are supplied to the pressure chamber 222, and the pressurechamber 223 surrounding the ring tube 209. Thus, the flanges 291 a arebrought into close contact with the semiconductor wafer W by pressurizedfluids supplied to the pressure chambers 222, 223. Accordingly, even ifpressure of the pressurized fluid supplied to the pressure chamber 222or 223 surrounding the pressure chamber 225 is considerably higher thanpressure of the pressurized fluid supplied to the pressure chamber 225defined in the ring tube 209, high-pressure fluid surrounding thepressure chamber 225 is prevented from flowing into a lower portion ofthe ring tube 209. Therefore, the flanges 291 a can widen a range ofpressure control in each of the pressure chambers, for thereby pressingthe semiconductor wafer more stably.

Openings 291 e are formed in central portions of the abutment portion291 b of the ring tube 209, and thus a pressurized fluid supplied to theintermediate pressure chamber 225 directly contacts with the uppersurface of the semiconductor wafer W through the openings 291 e of theabutment portion 291 b. Since a pressurized fluid is supplied to theintermediate pressure chamber 225 during polishing, the pressurizedfluid presses the abutment portion 291 b of the ring tube 209 againstthe upper surface of the semiconductor wafer W. Therefore, even if theopenings 291 e are formed in the abutment portion 291 b, a pressurizedfluid in the intermediate pressure chamber 225 hardly flows out to anexterior of the intermediate pressure chamber 225. Further, when thesemiconductor wafer W is released, a downward pressure can be appliedthrough the openings 291 e to the semiconductor wafer W by a pressurizedfluid, so that the semiconductor wafer W can more smoothly be released.

When the pressurized fluid supplied to the intermediate pressure chamber225 is controlled in terms of temperature and a temperature of thesemiconductor wafer W is controlled from a backside of the wafer to bepolished, as described above, the openings 291 e formed in the abutmentportion 291 b of the ring tube 209 can increase an area in which thepressurized fluid controlled in terms of temperature is brought intocontact with the semiconductor wafer W. Therefore, controllability interms of temperature of the semiconductor wafer W can be improved.Further, when polishing of the semiconductor wafer W is finished and thesemiconductor wafer W is released, the intermediate pressure chamber 225is opened to outside air via the openings 291 e. Thus, the fluidsupplied into the intermediate pressure chamber 225 is prevented fromremaining in the intermediate pressure chamber 225. Therefore, even ifsemiconductor wafers W are continuously polished, controllability interms of temperature of the semiconductor wafer W can be maintained.

In a case where the aforementioned flanges 291 a are provided at theabutment portion 291 b of the ring tube 209, when a pressurized fluid issupplied to the pressure chamber 221 to press the chucking plate 206downwardly for polishing, downward forces may excessively be applied toportions of the semiconductor wafer W near the base portions 291 d ofthe flanges 291 a of the ring tube 209 by the connecting portions 291 c,so that a polishing rate may be locally increased at these portions.

On the other hand, as shown in FIGS. 6A through 6C, in a case where,after the semiconductor wafer W is brought into close contact with theabutment portion 291 b of the ring tube 209, the pressure chamber 221 issupplied with a pressure smaller than a sum of pressing forces appliedto the pressure chambers 222 to 225 to polish the semiconductor wafer insuch a state that the chucking plate 206 is lifted, upward forces may beapplied to portions near the base portions 291 d of the flanges 291 awhich are brought into close contact with the semiconductor wafer W bythe connecting portions 291 c. Thus, a vacuum 293 may be formed near thebase portions 291 d (see FIG. 6C), so that a polishing rate may belocally lowered at these portions.

In view of the above, in the present embodiment, the connecting portions291 c of the ring tube 209 are made of a soft material having a higherflexibility than the abutment portion 291 b. With this configuration,even if the chucking plate 206 is downwardly pressed for polishing,excessive downward forces are not applied to the semiconductor wafer Wwhich is brought into close contact with the abutment portion 291 bbecause the connecting portions 291 c are likely to be elasticallydeformed, so that a uniform polishing rate can be achieved over anentire surface of the abutment portion 291 b except the flanges 291 a.Further, even if the chucking plate 206 is lifted for polishing,excessive upward forces are not applied to the abutment portion 291 bbecause the connecting portions 291 c are likely to extend. Thus, avacuum is not formed near the base portions 291 d of the flanges 291 a,so that a uniform polishing rate can be achieved over the entire surfaceof the abutment portion 291 b except the flanges 291 a. Only verticallyextending portions 291 f (see FIG. 5) of the connecting portions 291 cmay be made of a soft material having a high flexibility, or, inaddition thereto, portions 291 g held by the ring tube holder 292 mayalso be made of a soft material having a high flexibility.

FIG. 7 is a vertical cross-sectional view showing a second example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention. In the ring tube of the secondexample, connecting portions 291 c have thin portions 294 having athickness smaller than a thickness of abutment portion 291 b. The thinportions 294 are constricted inwardly as shown in FIG. 7. With such thinportions 294, even if chucking plate 206 is pressed downwardly forpolishing, excessive downward forces are not applied to semiconductorwafer W which is brought into close contact with the abutment portion291 b because the connecting portions 291 c are likely to be deformed atthe thin portions 294, so that a uniform polishing rate can be achievedover an entire surface of the abutment portion 291 b except flanges 291a. Further, even if the chucking plate 206 is lifted for polishing,excessive upward forces are not applied to the abutment portion 291 bbecause the thin portions 294 are likely to extend. Thus, a vacuum isnot formed near base portions 291 d of the flanges 291 a, so that auniform polishing rate can be achieved over the entire surface of theabutment portion 291 b except the flanges 291 a. Particularly, when thethin portions 294 are formed so as to be constricted inwardly incross-section, the above effects can effectively be achieved.

FIG. 8 is a vertical cross-sectional view showing a third example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention. In the ring tube of the thirdexample, intermediate members 295 having a low adhesiveness tosemiconductor wafer W are attached to lower surfaces of base portions291 d of flanges 291 a. Any member can be used as intermediate member295 as long as it has a low adhesiveness to the wafer W. For example, acellophane tape may be used as the intermediate member 295. Theintermediate member 295 should preferably be as thin as possible, andpreferably have a thickness of at most 0.2 mm. With this arrangement,even if the chucking plate 206 is lifted for polishing, a vacuum isunlikely to be formed near the base portions 291 d of the flanges 291 abecause the base portions 291 d of the flanges 291 a are unlikely to bebrought into close contact with the semiconductor wafer W. Therefore, auniform polishing rate can be achieved over an entire surface ofabutment portion 291 b except the flanges 291 a. Instead of mountingsuch intermediate members 295, adhesiveness between the base portions291 d of the flanges 291 a and the semiconductor wafer W may beweakened, for example, by forming a groove in lower surfaces of the baseportions 291 d of the flanges 291 a, or by forming the lower surfaces ofthe base portions 291 d as rough surfaces.

FIG. 9 is a vertical cross-sectional view showing a fourth example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention. In the ring tube of the fourthexample, ring-like hard members 296 made of a material harder thanelastic membrane 291 (e.g., stainless steel) are embedded in baseportions 291 d of flanges 291 a. With this arrangement, even if chuckingplate 206 is downwardly pressed for polishing, excessive downward forcesare not applied to semiconductor wafer W which is brought into closecontact with abutment portion 291 b because downward forces byconnecting portions 291 c are dispersed by the hard members 296, so thata uniform polishing rate can be achieved over an entire surface of theabutment portion 291 b except the flanges 291 a. Further, even ifchucking plate 206 is lifted for polishing, a vacuum is not formed nearthe base portions 291 d of the flanges 291 a because the hard members296 prevent deformation of the vicinity of the base portions 291 d ofthe flanges 291 a. Therefore, a uniform polishing rate can be achievedover the entire surface of the abutment portion 291 b except the flanges291 a.

FIG. 10 is a vertical cross-sectional view showing a fifth example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention. The fifth example corresponds to anexample of a ring tube in which a connecting portion 291 h positionedradially inwardly, i.e., near a center of semiconductor wafer W, has athickness smaller than that of a connecting portion 291 i positionedradially outwardly, in the elastic membrane 291 of the ring tube of thefirst example. Because a cylinder having a smaller curvature generallyhas a stiffness larger than a cylinder having a larger curvature, avertical force applied to the base portion of the flange by theconnecting portion positioned radially inwardly becomes larger than aforce applied to the base portion of the flange by the connectingportion positioned radially outwardly. Therefore, as shown in the fifthexample, when the connecting portion 291 h positioned radially inwardlyis thinner than the connecting portion 291 i positioned radiallyoutwardly, vertical forces applied to the base portions of the flangesby these connecting portions 291 h, 291 i can be adjusted to the samelevel, and a uniform polishing rate can be achieved over an entiresurface of abutment portion 291 b except flanges 291 a. When theconnecting portion positioned radially inwardly is made of a materialhaving a flexibility higher than that of material of the connectingportion positioned radially outwardly in the ring tube of the firstexample, similar effects are expected.

FIG. 11 is a vertical cross-sectional view showing a sixth example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention. The sixth example corresponds to anexample of a ring tube in which a flange 291 j projecting radiallyoutwardly has a length larger than a flange 291 k projecting radiallyinwardly, in the elastic membrane 291 of the ring tube of the firstexample. With this arrangement, a sealing capability can be enhanced atthe flange 291 j projecting radially outwardly, so that a uniformpolishing rate can be achieved over an entire surface of abutmentportion 291 b.

FIGS. 12A through 12C are vertical cross-sectional views showing aseventh example of a ring tube in a substrate holding apparatusaccording to the present invention. As shown in FIG. 12A, elasticmembrane 391 of the ring tube of the seventh example has an abutmentportion 391 b having flanges 391 a projecting outwardly, extendingportions 391 d extending outwardly from base portions 391 c of theflanges 391 a to form grooves 392 between the extending portions 391 dand the flanges 391 a, and connecting portions 391 e connected via ringtube holder 292 to chucking plate 206. The extending portions 391 dextend outwardly from the base portions 391 c of the flanges 391 a topositions inward of tips of the flanges 391 a, and the connectingportions 391 e extend upwardly from outward ends of the extendingportions 391 d. The flanges 391 a, the abutment portion 391 b, theconnecting portions 391 e, and the extending portions 391 d areintegrally made of the same material. An opening 391 f is formed in acentral portion of the abutment portion 391 b.

With this arrangement, in a case where the chucking plate 206 is liftedfor polishing after semiconductor wafer W is brought into close contactwith the abutment portion 391 b (see FIG. 12B), upward forces by theconnecting portions 391 e are converted into forces in horizontal oroblique directions by the extending portions 391 d, and these convertedforces are applied to the base portions 391 c of the flanges 391 a (seeFIG. 12C). Therefore, upward forces applied to the base portions 391 cof the flanges 391 a can be made extremely small, so that excessiveupward forces are not applied to the abutment portion 391 b.Accordingly, a vacuum is not formed near the base portions 391 d, sothat a uniform polishing rate can be achieved over an entire surface ofthe abutment portion 391 b except the flanges 391 a. In this case, athickness of the connecting portions 391 e or a length of the flanges391 a may be varied between the connecting portion disposed radiallyinwardly and the connecting portion disposed radially outwardly, as withthe ring tube in the fifth or sixth example. Further, the length of theextending portions 391 d may be varied between the extending portiondisposed radially inwardly and the extending portion disposed radiallyoutwardly. Furthermore, a thickness of the flanges 391 a may be variedaccording to a type of a film formed on a semiconductor wafer to bepolished or the polishing pad. When resistance or polishing torquetransmitted to the semiconductor wafer is large, the thickness of theflanges 391 a should preferably be made larger in order to preventtorsion of the flanges 391 a.

In the substrate holding apparatus according to the first embodimentdescribed above, the fluid passages 31, 33, 34, 35 and 36 are providedas separate passages. However, these fluid passages may be combined witheach other, or the pressure chambers may be communicated with each otherin accordance with a magnitude of a pressing force to be applied to thesemiconductor wafer W and a position to which the pressing force isapplied. In the first embodiment, the central bag 208 and the ring tube209 are brought into direct contact with the semiconductor wafer W.However, the present invention is not limited to such a configuration.For example, an elastic pad may be interposed between the central bag208 and ring tube 209 and the semiconductor wafer W so that the centralbag 208 and the ring tube 209 are brought into indirect contact with thesemiconductor wafer W. Further, the above examples may appropriately becombined with each other.

In the substrate holding apparatus according to the first embodimentdescribed above, the polishing surface is constituted by the polishingpad. However, the polishing surface is not limited to this. For example,the polishing surface may be constituted by a fixed abrasive. The fixedabrasive is formed into a flat plate comprising abrasive particles fixedby a binder. With the fixed abrasive used for polishing, a polishingprocess is performed by abrasive particles self-generated from the fixedabrasive. The fixed abrasive comprises abrasive particles, a binder, andpores. For example, cerium dioxide (CeO2) having an average particlediameter of 0.5 μm is used as an abrasive particle, and epoxy resin isused as a binder. Such a fixed abrasive forms a harder polishingsurface. The fixed abrasive includes a fixed abrasive pad having atwo-layer structure formed by a thin layer of a fixed abrasive and anelastic polishing pad attached to a lower surface of the layer of thefixed abrasive. IC-1000 described above may be used for another hardpolishing surface.

As described above, according to the substrate holding apparatus of thefirst embodiment of the present invention, pressures to be applied tothe substrate can independently be controlled, and hence a pressingforce applied to a thicker area of a thin film can be made higher than apressing force applied to a thinner area of the thin film, therebyselectively increasing a polishing rate of the thicker area of the thinfilm. Thus, an entire surface of a substrate can be polished exactly toa desired level irrespective of a film thickness distribution obtainedat a time the thin film is formed. Further, even if a vertically movablemember is pressed downwardly for polishing, excessive downward forcesare not applied to a substrate which is brought into close contact withthe abutment portion, so that a uniform polishing rate can be achievedin an area between the base portions of the flanges. Further, even if avertically movable member is lifted for polishing, excessive upwardforces are not applied to the abutment portion, so that a vacuum is notformed near the base portions of the flanges to achieve a uniformpolishing rate in an area between the base portions.

Next, a substrate holding apparatus according to a second embodiment ofthe present invention will be described below. FIG. 13 is a verticalcross-sectional view showing a top ring 1 as a substrate holdingapparatus according to the second embodiment of the present invention,and FIG. 14 is a bottom view showing the top ring 1 shown in FIG. 13. Asshown in FIG. 13, the top ring 1 constituting a substrate holdingapparatus comprises a top ring body 2 in the form of a cylindricalhousing with a receiving space defined therein, and a retainer ring 3fixed to a lower end of the top ring body 2. The top ring body 2 is madeof a material having high strength and rigidity, such as metal orceramic. The retainer ring 3 is made of highly rigid synthetic resin,ceramic, or the like.

The top ring body 2 comprises a cylindrical housing 2 a, an annularpressurizing sheet support 2 b fitted into a cylindrical portion of thehousing 2 a, and an annular seal 2 c fitted over an outercircumferential edge of an upper surface of the housing 2 a. Theretainer ring 3 is fixed to a lower end of the housing 2 a of the topring body 2. The retainer ring 3 has a lower portion projecting radiallyinwardly. The retainer ring 3 may be formed integrally with the top ringbody 2.

A top ring drive shaft 11 is disposed above a central portion of thehousing 2 a of the top ring body 2, and the top ring body 2 is coupledto the top ring drive shaft 11 by a universal joint 10. The universaljoint 10 has a spherical bearing mechanism by which the top ring body 2and the top ring drive shaft 11 are liftable with respect to each other,and a rotation transmitting mechanism for transmitting rotation of thetop ring drive shaft 11 to the top ring body 2. The spherical bearingmechanism and the rotation transmitting mechanism transmit a pressingforce and a rotating force from the top ring drive shaft 11 to the topring body 2 while allowing the top ring body 2 and the top ring driveshaft 11 to be tilted with respect to each other.

The spherical bearing mechanism comprises a hemispherical concave recess11 a defined centrally in a lower surface of the top ring drive shaft11, a hemispherical concave recess 2 d defined centrally in an uppersurface of the housing 2 a, and a ball bearing 12 made of a highly hardmaterial such as ceramic and interposed between the concave recesses 11a and 2 d. On the other hand, the rotation transmitting mechanismcomprises drive pins (not shown) fixed to the top ring drive shaft 11,and driven pins (not shown) fixed to the housing 2 a. Even if the topring body 2 is tilted with respect to the top ring drive shaft 11, thedrive pins and the driven pins remain in engagement with each otherwhile contact points are displaced because the drive pins and the drivenpins are vertically movable relatively to each other. Thus, the rotationtransmitting mechanism reliably transmits rotational torque of the topring drive shaft 11 to the top ring body 2.

The top ring body 2 and the retainer ring 3 secured to the top ring body2 have a space defined therein, which accommodates therein a seal ring404 having a lower surface brought into contact with a peripheralportion of a semiconductor wafer W held by the top ring 1, an annularholder ring 405, and a disk-shaped chucking plate 406 (verticallymovable member) which is vertically movable within the receiving spacein the top ring body 2.

The seal ring 404 has a radially outer edge clamped between the holderring 405 and the chucking plate 406 secured to a lower end of the holderring 405 and extends radially inwardly so as to cover a lower surface ofthe chucking plate 406 near its outer circumferential edge. A lower endsurface of the seal ring 404 is brought into contact with an uppersurface of semiconductor wafer W to be polished. The seal ring 404 ismade of a highly strong and durable rubber material such as ethylenepropylene rubber (EPDM), polyurethane rubber, or silicone rubber. Thesemiconductor wafer W has a recess defined in an outer edge thereof,which is referred to as a notch or orientation flat, for recognizing(identifying) an orientation of the semiconductor wafer. The seal ring404 should preferably extend radially inwardly of the chucking plate 406from an innermost position of such a notch or orientation flat.

A pressurizing sheet 407 comprising an elastic membrane extends betweenthe holder ring 405 and the top ring body 2. The pressurizing sheet 407has a radially outer edge clamped between the housing 2 a and thepressurizing sheet support 2 b of the top ring body 2, and a radiallyinner edge clamped between an upper end portion 405 a and a stopper 405b of the holder ring 405. The top ring body 2, the chucking plate 406,the holder ring 405, and the pressurizing sheet 407 jointly define apressure chamber 421 in the top ring body 2. As shown in FIG. 13, afluid passage 31 comprising tubes and connectors communicates with thepressure chamber 421, which is connected to a compressed air source 120via a regulator R2 provided on the fluid passage 31 (see FIG. 1). Thepressurizing sheet 407 is made of a highly strong and durable rubbermaterial such as ethylene propylene rubber (EPDM), polyurethane rubber,or silicone rubber.

In a case where the pressurizing sheet 407 is made of an elasticmaterial such as rubber, if the pressurizing sheet 407 is fixedlyclamped between the retainer ring 3 and the top ring body 2, then adesired horizontal surface cannot be maintained on a lower surface ofthe retainer ring 3 because of elastic deformation of the pressurizingsheet 407 as an elastic material. In order to prevent such a drawback,the pressurizing sheet 407 is clamped between the housing 2 a of the topring body 2 and the pressurizing sheet support 2 b provided as aseparate member in the present embodiment. The retainer ring 3 mayvertically be movable with respect to the top ring body 2, or theretainer ring 3 may have a structure capable of pressing the polishingsurface independently of the top ring body 2. In such cases, thepressurizing sheet 407 is not necessarily fixed in the aforementionedmanner.

A cleaning liquid passage 451 in the form of an annular groove isdefined in an upper surface of the housing 2 a near its outercircumferential edge over which the seal 2 c of the top ring body 2 isfitted. The cleaning liquid passage 451 communicates with a fluidpassage 32 via a through-hole 452, and is supplied with a cleaningliquid (pure water) via the fluid passage 32. A plurality ofcommunication holes 453 is defined in the housing 2 a and thepressurizing sheet support 2 b in communication with the cleaning liquidpassage 451. The communication holes 453 communicate with a small gap Gdefined between an outer circumferential surface of the seal ring 404and an inner circumferential surface of the retainer ring 3.

The chucking plate 406 has a central port 408 provided on a lowersurface of a central portion of the chucking plate 406, with an opening408 a defined at a central portion of the central port 408. A ring tube409 which serves as an abutment member brought into contact with thesemiconductor wafer W is mounted in a space defined between the chuckingplate 406 and the semiconductor wafer W. In the present embodiment, asshown in FIGS. 13 and 14, the ring tube 409 is disposed radiallyoutwardly of the central port 408 in a surrounding relation relativethereto. The chucking plate 406 has suction portions 440 extendeddownwardly therefrom outside of the ring tube 409. In the presentembodiment, six suction portions 440 are provided.

The ring tube 409 comprises an elastic membrane 491 brought into contactwith an upper surface of the semiconductor wafer W, and a ring tubeholder 492 for detachably holding the elastic membrane 491 in position.The ring tube 409 has a pressure chamber 422 defined therein by theelastic membrane 491 and the ring tube holder 492. A space definedbetween the chucking plate 406 and the semiconductor wafer W is dividedinto a plurality of spaces by the ring tube 409. Accordingly, a pressurechamber 423 is defined radially inwardly of the ring tube 409, i.e.,around the central port 408, and a pressure chamber 424 is definedradially outwardly of the ring tube 409, i.e., around the suctionportions 440. The elastic membrane 491 of the ring tube 409 is made of ahighly strong and durable rubber material such as ethylene propylenerubber (EPDM), polyurethane rubber, or silicone rubber, as with thepressurizing sheet 407.

A fluid passage 33 comprising tubes and connectors communicates with thepressure chamber 422 in the ring tube 409. The pressure chamber 422 isconnected to the compressed air source 120 via a regulator R3 connectedto the fluid passage 33. A fluid passage 34 comprising tubes andconnectors communicates with the opening 408 a of the central port 408.The central port 408 is connected to the compressed air source 120 via aregulator R4 connected to the fluid passage 34. Each suction portion 440has a communication hole 440 a communicating with a fluid passage 35comprising tubes and connectors. The suction portions 440 are connectedto the compressed air source 120 via a regulator R5 connected to thefluid passages 35. The compressed air source 120 develops a negativepressure at opening ends of communication holes 440 a of the suctionportions 440 to attract a semiconductor wafer W to the suction portions440. The suction portions 440 have elastic sheets 440 b, such as thinrubber sheets, attached to their lower ends, for thereby elasticallycontacting and holding the semiconductor wafer W on lower surfacesthereof. The pressure chambers 421 to 424 are connected to respectiveregulators R2 to R5 through a rotary joint (not shown) mounted on anupper end of the top ring shaft 110.

The pressure chamber 421 above the chucking plate 406 and the pressurechambers 422, 423, 424 are supplied with pressurized fluids such aspressurized air or atmospheric air or evacuated, via the fluid passages31, 33, 34 and 35 connected to respective pressure chambers. As shown inFIG. 1, the regulators R2 to R5 connected to the fluid passages 31, 33,34 and 35 of the pressure chambers 421 to 424 can respectively regulatepressures of the pressurized fluids supplied to the respective pressurechambers. Thus, it is possible to independently control pressures in thepressure chambers 421 to 424 or independently introduce atmospheric airor vacuum into the pressure chambers 421 to 424. In this manner, thepressures in the pressure chambers 421 to 424 are independently variedwith the regulators R2 to R5, so that pressing forces to press thesemiconductor wafer W against polishing pad 101 can be adjusted in localareas of the semiconductor wafer W.

In this case, pressurized fluid or atmospheric air supplied to thepressure chambers 422 to 424 may independently be controlled in terms oftemperature. With this configuration, it is possible to directly controltemperature of a workpiece such as a semiconductor wafer from a backsideof the surface to be polished. Particularly, when each of the pressurechambers is independently controlled in terms of temperature, a rate ofchemical reaction can be controlled during chemical polishing process ofCMP.

Since there is a small gap G between the outer circumferential surfaceof the seal ring 404 and the inner circumferential surface of theretainer ring 3, the holder ring 405, the chucking plate 406, and theseal ring 404 attached to the chucking plate 406 can vertically be movedwith respect to the top ring body 2 and the retainer ring 3, and henceare of a floating structure with respect to the top ring body 2 and theretainer ring 3. The stopper 405 b of the holder ring 405 has aplurality of teeth 405 c projecting radially outwardly from an outercircumferential edge thereof. Downward movement of members including theholder ring 405 is limited to a predetermined range by engaging theteeth 405 c with an upper surface of a radially inwardly projectingportion of the retainer ring 3.

For example, in a case where the chucking plate is made of PPS(polyphenylene sulfide), if pressure in the pressure chamber 421 ishigher than pressures in the pressure chambers 422 to 424 below thechucking plate 406, the chucking plate is bent so that the suctionportions 440 press the semiconductor wafer W to increase polishing ratesat those local areas. Accordingly, the chucking plate 406 in the presentembodiment is made of a material having a larger stiffness and a lighterweight than that of PPS, e.g., epoxy resin, preferably a fiberreinforced material such as a glass fiber reinforced material. Thus,with the chucking plate 406 made of a material having a large stiffness,even if the pressure in the pressure chamber 421 is higher than thepressures in the pressure chambers 422 to 424 below the chucking plate406, the chucking plate 406 becomes unlikely to be bent, so thatpolishing rates are prevented from being locally increased.Particularly, since epoxy resin has no magnetism, it is suitable forcases where a film thickness of a thin film formed on a surface of asemiconductor wafer to be polished is measured with a film thicknessmethod using eddy current in such a state that the semiconductor waferis held by a top ring. The material is not limited to epoxy resin, andit is also effective to use other resin having a large stiffness, fiberreinforced materials thereof, or ceramics.

Next, operation of the top ring 1 thus constructed will be described indetail below.

In the polishing apparatus constructed above, when a semiconductor waferW is to be delivered to the polishing apparatus, the top ring 1 as awhole is moved to a position to which the semiconductor wafer W istransferred, and the communication holes 440 a of the suction portions440 are connected via the fluid passage 35 to the vacuum source 121. Thesemiconductor wafer W is attracted under vacuum to lower ends of thesuction portions 440 by suction effect of the communication holes 440 a.With the semiconductor wafer W attracted to the top ring 1, the top ring1 as a whole is moved to a position above the polishing table 100 havinga polishing surface (polishing pad 101) thereon. An outercircumferential edge of the semiconductor wafer W is held by theretainer ring 3 so that the semiconductor wafer W is not removed fromthe top ring 1.

For polishing the semiconductor wafer W, attraction of semiconductorwafer W by the suction portions 440 is released, and the semiconductorwafer W is held on a lower surface of the top ring 1. Simultaneously,top ring air cylinder 111 connected to the top ring drive shaft 11 isactuated to press the retainer ring 3 fixed to the lower end of the topring 1 against the polishing surface on the polishing table 100 under apredetermined pressure (see FIG. 1). In such a state, pressurized fluidsare respectively supplied to the pressure chambers 422, 423, 424 underrespective pressures, thereby pressing the semiconductor wafer W againstthe polishing surface on the polishing table 100. Polishing liquidsupply nozzle 102 supplies a polishing liquid Q onto the polishing pad101 in advance, so that the polishing liquid Q is held on the polishingpad 101. Thus, the semiconductor wafer W is polished by the polishingpad 101 with the polishing liquid Q being present between a (lower)surface, to be polished, of the semiconductor wafer W and the polishingpad 101.

Local areas of the semiconductor wafer W that are positioned beneath thepressure chambers 423, 424 are pressed against the polishing surfaceunder pressures of the pressurized fluids supplied to the pressurechambers 423, 424. A local area of the semiconductor wafer W that ispositioned beneath the central pressure chamber 422 is pressed via theelastic membrane 491 of the ring tube 409 against the polishing surfaceunder pressure of the pressurized fluid supplied to the pressure chamber422. Therefore, polishing pressures acting on respective local areas ofthe semiconductor wafer W can be adjusted independently by controllingpressures of the pressurized fluids supplied to the respective pressurechambers 422 to 424. Specifically, the respective regulators R3 to R5independently regulate the pressures of the pressurized fluids suppliedto the pressure chambers 422 to 424 for thereby adjusting the pressingforces applied to press the local areas of the semiconductor wafer Wagainst the polishing pad 101 on the polishing table 100. With thepolishing pressures on the respective local areas of the semiconductorwafer W being adjusted independently to desired values, thesemiconductor wafer W is pressed against the polishing pad 101 on thepolishing table 100 that is being rotated. Similarly, pressure of thepressurized fluid supplied to the top ring air cylinder 111 can beregulated by the regulator R1 to adjust a force with which the retainerring 3 presses the polishing pad 101. While the semiconductor wafer W isbeing polished, the force with which the retainer ring 3 presses thepolishing pad 101 and the pressing force with which the semiconductorwafer W is pressed against the polishing pad 101 can appropriately beadjusted for thereby applying polishing pressures in a desired pressuredistribution to a central area (C1 in FIG. 14), an intermediate area(C2), a peripheral area (C3), and a peripheral portion of the retainerring 3 which is positioned outside of the semiconductor wafer W.

In this manner, the semiconductor wafer W is divided into threeconcentric circular and annular areas (C1 to C3), which can respectivelybe pressed under independent pressing forces. A polishing rate dependson a pressing force applied to a semiconductor wafer W against apolishing surface. As described above, since the pressing forces appliedto those areas can independently be controlled, polishing rates of thethree circular and annular areas (C1 to C3) of the semiconductor wafer Wcan independently be controlled. Consequently, even if a thickness of athin film to be polished on a surface of the semiconductor wafer Wsuffers radial variations, the thin film on the surface of thesemiconductor wafer W can be polished uniformly without beinginsufficiently or excessively polished over an entire surface of thesemiconductor wafer. More specifically, even if the thickness of thethin film to be polished on the surface of the semiconductor wafer Wdiffers depending on a radial position on the semiconductor wafer W,pressure in a pressure chamber positioned over a thicker area of thethin film is made higher than pressure in other pressure chambers, orpressure in a pressure chamber positioned over a thinner area of thethin film is made lower than pressure in other pressure chambers. Inthis manner, a pressing force applied to the thicker area of the thinfilm against the polishing surface is made higher than a pressing forceapplied to the thinner area of the thin film against the polishingsurface, thereby selectively increasing a polishing rate of the thickerarea of the thin film. Consequently, an entire surface of thesemiconductor wafer W can be polished exactly to a desired level overthe entire surface of the semiconductor wafer W irrespective of a filmthickness distribution produced at a time the thin film is formed.

Any unwanted edge rounding on a circumferential edge of thesemiconductor wafer W can be prevented by controlling the pressing forceapplied to the retainer ring 3. If the thin film to be polished on thecircumferential edge of the semiconductor wafer W has large thicknessvariations, then the pressing force applied to the retainer ring 3 isintentionally increased or reduced to thus control a polishing rate ofthe circumferential edge of the semiconductor wafer W. When pressurizedfluids are supplied to the pressure chambers 422 to 424, the chuckingplate 406 is subjected to upward forces. In the present embodiment, thepressurized fluid is supplied to the pressure chamber 421 via the fluidpassage 31 to prevent the chucking plate 406 from being lifted underforces due to the pressure chambers 422 to 424.

As described above, the pressing force applied by the top ring aircylinder 111 to press the retainer ring 3 against the polishing pad 101and the pressing forces applied by the pressurized air supplied to thepressure chambers 422 to 424 to press the local areas of thesemiconductor wafer W against the polishing pad 101 are appropriatelyadjusted to polish the semiconductor wafer W. When polishing of thesemiconductor wafer W is finished, the semiconductor wafer W isattracted again to the lower ends of the suction portions 440 undervacuum. At this time, supply of the pressurized fluids into the pressurechambers 422 to 424 to press the semiconductor wafer W against thepolishing surface is stopped, and the pressure chambers 422 to 424 arevented to an atmosphere. Accordingly, the lower ends of the suctionportions 440 are brought into contact with the semiconductor wafer W.The pressure chamber 421 is vented to the atmosphere or evacuated todevelop a negative pressure therein. If the pressure chamber 421 ismaintained at a high pressure, then the semiconductor wafer W isstrongly pressed against the polishing surface only in areas broughtinto contact with the suction portions 440.

After attraction of the semiconductor wafer W, the top ring 1 as a wholeis moved to a position to which the semiconductor wafer W is to betransferred, and then a fluid (e.g., compressed air or a mixture ofnitrogen and pure water) is ejected to the semiconductor wafer W via thecommunication holes 440 a of the suction portions 440 to release thesemiconductor wafer W from the top ring 1.

The polishing liquid Q used to polish the semiconductor wafer W tends toflow through the small gap G between the outer circumferential surfaceof the seal ring 404 and the retainer ring 3. If the polishing liquid Qis firmly deposited in the gap G, then the holder ring 405, the chuckingplate 406, and the seal ring 404 are prevented from smoothly movingvertically with respect to the top ring body 2 and the retainer ring 3.To avoid such a drawback, a cleaning liquid (pure water) is suppliedthrough the fluid passage 32 to the cleaning liquid passage 451.Accordingly, the pure water is supplied via a plurality of communicationholes 453 to a region above the gap G, thus cleaning the gap G toprevent the polishing liquid Q from being firmly deposited in the gap G.The pure water should preferably be supplied after a polishedsemiconductor wafer W is released and not until a next semiconductorwafer to be polished is attracted to the top ring 1. It is alsopreferable to discharge all supplied pure water out of the top ring 1before the next semiconductor wafer is polished, and hence to providethe retainer ring 3 with a plurality of through-holes 3 a shown in FIG.13. Furthermore, if a pressure buildup is developed in a space 425defined between the retainer ring 3, the holder ring 405, and thepressurizing sheet 407, then it acts to prevent the chucking plate 406from being elevated in the top ring body 2. Therefore, in order to allowthe chucking plate 406 to be elevated smoothly in the top ring body 2,the through-holes 3 a should preferably be provided for equalizingpressure in the space 425 with atmospheric pressure.

As described above, according to a substrate holding apparatus of thesecond embodiment, pressures in the pressure chambers 422, 423, 424 areindependently controlled to control pressing forces acting on thesemiconductor wafer W.

The ring tube 409 of the substrate holding apparatus according to thesecond embodiment of the present invention will be described in detailbelow.

FIG. 15 is a vertical cross-sectional view showing the ring tube 409shown in FIG. 13. As shown in FIG. 15, the elastic membrane 491 of thering tube 409 in the present embodiment has an abutment portion 491 bhaving flanges 491 a projecting outwardly and inwardly, and connectingportions 491 c connected via the ring tube holder 492 to the chuckingplate 406. The connecting portions 491 c extend upwardly from baseportions 491 d of the flanges 491 a. A lower surface of the abutmentportion 491 b is brought into contact with the upper surface of thesemiconductor wafer W. The flanges 491 a, the abutment portion 491 b,and the connecting portions 491 c are integrally made of the samematerial.

As described above, when a semiconductor wafer is polished, pressurizedfluids are supplied to the pressure chamber 422, and the pressurechambers 423, 424 surrounding the ring tube 409. Thus, the flanges 491 aare brought into close contact with the semiconductor wafer W by thepressurized fluids supplied to the pressure chambers 423, 424.Accordingly, even if pressure of the pressurized fluid supplied to thepressure chamber 423 or 424 surrounding the pressure chamber 422 isconsiderably higher than pressure of the pressurized fluid supplied tothe pressure chamber 422 defined in the ring tube 409, high-pressurefluid surrounding the pressure chamber 422 is prevented from flowinginto a lower portion of the ring tube 409. Therefore, the flanges 491 acan widen a range of pressure control in each of the pressure chambers,for thereby pressing the semiconductor wafer more stably.

Openings 491 e are formed at a plurality of central portions of theabutment portion 491 b of the ring tube 409, and thus a pressurizedfluid supplied to the pressure chamber 422 directly contacts with theupper surface of the semiconductor wafer W through the openings 491 e ofthe abutment portion 491 b. Since a pressurized fluid is supplied to thepressure chamber 422 during polishing, the pressurized fluid presses theabutment portion 491 b of the ring tube 409 against the upper surface ofthe semiconductor wafer W. Therefore, even if the openings 491 e areformed in the abutment portion 491 b, a pressurized fluid in thepressure chamber 422 hardly flows out to an exterior of the pressurechamber 422. Further, when the semiconductor wafer W is released, adownward pressure can be applied through the openings 491 e to thesemiconductor wafer W by a pressurized fluid, so that the semiconductorwafer W can more smoothly be released.

When the pressurized fluid supplied to the intermediate pressure chamber422 is controlled in terms of temperature and a temperature of thesemiconductor wafer W is controlled from the backside of the surface tobe polished, as described above, the openings 491 e formed in theabutment portion 491 b of the ring tube 409 can increase an area inwhich the pressurized fluid controlled in terms of temperature isbrought into contact with the semiconductor wafer W. Therefore,controllability in terms of temperature of the semiconductor wafer W canbe improved. Further, when polishing of the semiconductor wafer W isfinished and the semiconductor wafer W is released, the pressure chamber422 is opened to outside air via the openings 491 e. Thus, fluidsupplied into the pressure chamber 422 is prevented from remaining inthe pressure chamber 422. Therefore, even if semiconductor wafers W arecontinuously polished, controllability in terms of temperature of thesemiconductor wafer W can be maintained.

As shown in FIG. 15, the chucking plate 406 has support portions 406 afor supporting the flanges 491 a of the ring tube 409. If the chuckingplate 406 has no support portions 406 a, then the flanges 491 a may bedeformed and attached to a lower surface of the chucking plate 406 asshown in FIG. 16 when pressurized fluids are supplied to the pressurechambers 423, 424 surrounding the ring tube 409. In such a state, it isimpossible to properly control pressures of the pressure chambers 422 to424. Accordingly, in the present embodiment, the support portions 406 aare provided on the chucking plate 406 for supporting the flanges 491 aof the ring tube 409, as described above, to prevent the flanges 491 afrom being attached to the lower surface of the chucking plate 406 andto stabilize pressures of the pressure chambers 422 to 424. In thiscase, when the support portions have radial lengths larger than radiallengths of the flanges 491 a, it is possible to support the flanges 491a more reliably.

In this case, the flanges 491 a of the ring tube 409 are brought intocontact with the support portions 406 a of the chucking plate 406. Inorder to enhance adhesiveness of the flanges 491 a to the semiconductorwafer W, it is necessary to press the flanges 491 a by pressurizedfluids supplied to the pressure chambers 423, 424. Accordingly, in thepresent embodiment, as shown in FIG. 17, fluid introduction grooves 406b are formed in the support portions 406 a of the chucking plate 406 forstably pressing the flanges 491 a by pressurized fluids supplied to thepressure chambers 423, 424 to enhance adhesiveness between the flanges491 a and the semiconductor wafer W.

Similarly, with respect to the seal ring 404, the seal ring 404 may beattached to a peripheral portion of the chucking plate 406 by apressurized fluid supplied to the pressure chamber 424, as shown in FIG.18. Accordingly, in the present embodiment, a support portion 406 c isprovided at a peripheral portion of the chucking plate 406 forsupporting the seal ring 404, as shown in FIG. 19. In this case, as withthe support portions 406 a, fluid introduction grooves may be formed inthe support portion 406 c for stably pressing the seal ring 404 by apressurized fluid supplied to the pressure chamber 424 to enhanceadhesiveness between the seal ring 404 and the semiconductor wafer W.Further, since such grooves can introduce pressurized fluid to anoutermost portion of a semiconductor wafer, a uniform pressing force canbe achieved at a peripheral portion of the wafer.

When the retainer ring 3 is pressed against the polishing pad 101, thepolishing pad 101 may be raised (rebounded) near the retainer ring 3 sothat a polishing rate is locally increased at the peripheral portion ofsemiconductor wafer W. In the present embodiment, a radial length d ofthe support portion 406 c of the chucking plate 406 is shortened toprevent the semiconductor wafer W from being excessively polished at theperipheral portion thereof. When effects of rebound are small, thelength d is shortened to concentrate pressing forces, or the length d islengthened to disperse the pressing forces, for varying polishing rates.Specifically, the length d is varied in a range of 1 mm to 7 mm toachieve desired polishing rates.

In the substrate holding apparatus according to the second embodimentdescribed above, the fluid passages 31, 33, 34 and 35 are provided asseparate passages. However, these fluid passages may be combined witheach other, or the pressure chambers may be communicated with each otherin accordance with a magnitude of a pressing force to be applied to thesemiconductor wafer W and a position to which the pressing force isapplied. In the above embodiment, the ring tube 409 is brought intodirect contact with the semiconductor wafer W. However, the presentinvention is not limited to such a configuration. For example, anelastic pad may be interposed between the ring tube 409 and thesemiconductor wafer W so that the ring tube 409 is brought into indirectcontact with the semiconductor wafer W.

In the second embodiment shown in FIGS. 13 through 19, the polishingsurface is constituted by the polishing pad. However, the polishingsurface is not limited to this. The polishing surface may be constitutedby a fixed abrasive as described in the first embodiment shown in FIGS.2 through 12.

As described above, according to the substrate holding apparatus of thesecond embodiment of the present invention, pressures to be applied to asubstrate can independently be controlled, and hence a pressing forceapplied to a thicker area of a thin film can be made higher than apressing force applied to a thinner area of the thin film, therebyselectively increasing a polishing rate of the thicker area of the thinfilm. Thus, an entire surface of a substrate can be polished exactly toa desired level irrespective of a film thickness distribution obtainedat a time the thin film is formed. Further, with a vertically movablemember made of a material having a large stiffness and a light weight,e.g., epoxy resin, the vertically movable member becomes unlikely to bebent, so that polishing rates are prevented from being locallyincreased. Further, when a material having no magnetism is selected as amaterial of the vertically movable member, it is suitable for caseswhere a film thickness of a thin film formed on a surface of asemiconductor wafer to be polished is measured with a film thicknessmethod using eddy current in such a state that the semiconductor waferis held by a top ring.

Next, a substrate holding apparatus according to a third embodiment ofthe present invention will be described below. FIG. 20 is a verticalcross-sectional view showing a top ring 1 according to the thirdembodiment of the present invention. As shown in FIG. 20, the top ring 1constituting a substrate holding apparatus comprises a top ring body 2in the form of a cylindrical housing with a receiving space definedtherein, and a retainer ring 3 fixed to a lower end of the top ring body2. The top ring body 2 is made of a material having high strength andrigidity, such as metal or ceramic. The retainer ring 3 is made ofhighly rigid synthetic resin, ceramic, or the like.

The top ring body 2 comprises a cylindrical housing 2 a, an annularpressurizing sheet support 2 b fitted into a cylindrical portion of thehousing 2 a, and an annular seal 2 c fitted over an outercircumferential edge of an upper surface of the housing 2 a. Theretainer ring 3 is fixed to a lower end of the housing 2 a of the topring body 2. The retainer ring 3 has a lower portion projecting radiallyinwardly. The retainer ring 3 may be formed integrally with the top ringbody 2.

A top ring drive shaft 11 is disposed above a central portion of thehousing 2 a of the top ring body 2, and the top ring body 2 is coupledto the top ring drive shaft 11 by a universal joint 10. The universaljoint 10 has a spherical bearing mechanism by which the top ring body 2and the top ring drive shaft 11 are tiltable with respect to each other,and a rotation transmitting mechanism for transmitting rotation of thetop ring drive shaft 11 to the top ring body 2. The spherical bearingmechanism and the rotation transmitting mechanism transmit a pressingforce and a rotating force from the top ring drive shaft 11 to the topring body 2 while allowing the top ring body 2 and the top ring driveshaft 11 to be tilted with respect to each other.

The top ring body 2 and the retainer ring 3 secured to the top ring body2 have a space defined therein, which accommodates therein an edge bag504 having a lower surface brought into contact with a peripheralportion of a semiconductor wafer W held by the top ring 1, a holder ring505, a disk-shaped chucking plate 506 which is vertically movable withinthe receiving space in the top ring body 2, and a torque transmittingmember 507 having a lower surface brought into contact with thesemiconductor wafer W at a radially inward position of the edge bag 504.

The chucking plate 506 may be made of metal. However, when a thicknessof a thin film formed on a surface of a semiconductor wafer to bepolished is measured by a method using eddy current in such a state thatthe semiconductor wafer is held by the top ring, the chucking plate 506should preferably be made of a non-magnetic material, e.g., aninsulating material such as fluororesin or ceramic.

A pressurizing sheet 508 comprising an elastic membrane extends betweenthe holder ring 505 and the top ring body 2. The pressurizing sheet 508has a radially outer edge clamped between the housing 2 a and thepressurizing sheet support 2 b of the top ring body 2, and a radiallyinner edge clamped between an upper end portion 505 a and a stopper 505b of the holder ring 505. The top ring body 2, the chucking plate 506,the holder ring 505, and the pressurizing sheet 508 jointly define apressure chamber 521 in the top ring body 2. As shown in FIG. 20, afluid passage 31 comprising tubes and connectors communicates with thepressure chamber 521, which is connected to a compressed air source 120via a regulator R2 provided on the fluid passage 31 (see FIG. 1). Thepressurizing sheet 508 is made of a highly strong and durable rubbermaterial such as ethylene propylene rubber (EPDM), polyurethane rubber,or silicone rubber.

A cleaning liquid passage 551 in the form of an annular groove isdefined in an upper surface of the housing 2 a near its outercircumferential edge over which the seal 2 c of the top ring body 2 isfitted. The cleaning liquid passage 551 communicates with a fluidpassage 32 via a through-hole formed in the seal 2 c, and is suppliedwith a cleaning liquid (pure water) via the fluid passage 32. Aplurality of communication holes 553 are defined in the housing 2 a andthe pressurizing sheet support 2 b in communication with the cleaningliquid passage 551. The communication holes 553 communicate with a smallgap G defined between an outer circumferential surface of the edge bag504 and an inner circumferential surface of the retainer ring 3.

FIG. 21 is a partial cross-sectional view showing the edge bag 504 ofFIG. 20. As shown in FIG. 21, the edge bag 504 has a radially outer edgeclamped between the stopper 505 b of the holder ring 505 and an edge bagholder 506 a disposed below the holder ring 505, and a radially inneredge clamped between the edge bag holder 506 a and a chucking plate body506 b. A lower end surface of the edge bag 504 is brought into contactwith a peripheral portion of the semiconductor wafer W to be polished.The edge bag 504 comprises an elastic membrane made of a highly strongand durable rubber material such as ethylene propylene rubber (EPDM),polyurethane rubber, or silicone rubber.

A lower surface of the edge bag 504 is brought into contact with theperipheral portion of the semiconductor wafer W and provided with aflange 541 projecting radially inwardly. The edge bag 504 has a (first)pressure chamber 522 defined therein by the elastic membrane. A fluidpassage 33 comprising tubes and connectors communicates with thepressure chamber 522. The pressure chamber 522 is connected to thecompressed air source 120 via a regulator R3 connected to the fluidpassages 33.

Upon polishing, semiconductor wafer W is rotated in accordance withrotation of the top ring 1. Since the aforementioned edge bag 504 has asmall contact area with the semiconductor wafer W, rotational torque mayfail to completely be transmitted to the semiconductor wafer W.Accordingly, the torque transmitting member 507 is secured to thechucking plate 506 for transmitting sufficient torque to thesemiconductor wafer W by abutment with the semiconductor wafer W. Thetorque transmitting member 507 is in the form of an annular bag and isbrought into contact with the semiconductor wafer W with a contact arealarge enough to transmit sufficient torque to the semiconductor wafer W.

FIG. 22 is a partial cross-sectional view showing the torquetransmitting member 507 of FIG. 20. As shown in FIG. 22, the torquetransmitting member 507 comprises an elastic membrane 571 brought intocontact with the upper surface of the semiconductor wafer W, and atorque transmitting member holder 572 for detachably holding the elasticmembrane 571 in position. The torque transmitting member 507 has a space560 defined therein by the elastic membrane 571 and the torquetransmitting member holder 572. The elastic membrane 571 of the torquetransmitting member 507 is made of a highly strong and durable rubbermaterial such as ethylene propylene rubber (EPDM), polyurethane rubber,or silicone rubber, as with the edge bag 504.

As shown in FIG. 22, the elastic membrane 571 of the torque transmittingmember 507 has an abutment portion 571 b having flanges 571 a projectingoutwardly and inwardly, and connecting portions 571 c connected via thetorque transmitting member holder 572 to the chucking plate 506. Twoconnecting portions 571 c extend upwardly from base portions 571 d ofthe flanges 571 a. A lower surface of the abutment portion 571 b isbrought into contact with an upper surface of the semiconductor wafer W.The connecting portions 571 c have a plurality of communication holes573 provided at radially inward and outward positions, and an interiorof internal space 560 of the torque transmitting member 507 iscommunicated with external spaces 561, 562.

When the two connecting portions 571 c extending vertically are arrangedat relatively near positions, the connecting portions 571 c havesufficient strength to transmit torque. With the flanges 571 a, it ispossible to maintain a contact area with the semiconductor wafer W.

The space defined between the chucking plate 506 and the semiconductorwafer W is divided into a plurality of spaces, i.e., a pressure chamber522 disposed radially inwardly of the edge bag 504, the space 560 in thetorque transmitting member 507, a space 561 between the edge bag 504 andthe torque transmitting member 507, and a space 562 disposed radiallyinwardly of the torque transmitting member 507. As described above, thecommunication holes 573 are provided in the connecting portions 571 c ofthe torque transmitting member 507. Accordingly, the space 561, thespace 560, and the space 562 are communicated with each other throughthe communication holes 573, so that a (second) pressure chamber 523 isformed radially inwardly of the edge bag 504.

A fluid passage 34 comprising tubes and connectors communicates with thespace 560 in the torque transmitting member 507. The space 560 isconnected to the compressed air source 120 via a regulator R4 connectedto the fluid passage 34. A fluid passage 35 comprising tubes andconnectors communicates with the space 561 between the edge bag 504 andthe torque transmitting member 507. The space 561 is connected to thecompressed air source 120 via a regulator R5 connected to the fluidpassage 35. A fluid passage 36 comprising tubes and connectorscommunicates with the space 562 disposed radially inwardly of the torquetransmitting member 507. The space 562 is connected to the compressedair source 120 via a regulator (not shown) connected to the fluidpassage 36. The pressure chambers 521 to 523 are connected to respectiveregulators through a rotary joint (not shown) mounted on an upper end oftop ring shaft 110.

Since the space 561, the space 560, and the space 562 are communicatedwith each other, as described above, one fluid passage can supply apressurized fluid so as to uniformly control pressure of the pressurechamber 523 without a plurality of fluid passages. However, in order toobtain good responsiveness when pressure of the pressure chamber 523 isvaried, it is desirable to provide a plurality of fluid passages 34, 35,36 as described in the third embodiment. It is not necessary to provideregulators for respective fluid passages 34, 35, 36, and the fluidpassages 34, 35, 36 may be connected to one regulator to controlpressure.

When the semiconductor wafer is polished, pressurized fluids aresupplied to the pressure chamber 522 and the pressure chamber 523,respectively. The flange 541 is provided at a lower end surface of theedge bag 504. The flange 541 is brought into close contact with thesemiconductor wafer W by the pressurized fluid supplied to the pressurechamber 523. Accordingly, the pressurized fluid in the pressure chamber523 is prevented from flowing into a lower portion of the edge bag 504.Therefore, the flange 541 can realize a stable control when pressures ofthe pressure chamber 522 and the pressure chamber 523 are varied. Here,a radial width d of the elastic membrane defining the pressure chamber522 in the edge bag 504 should preferably be in a range of from about 1mm to about 10 mm in view of controlling a polishing rate at aperipheral portion of the semiconductor wafer W, and is set to be 5 mmin the present embodiment.

The pressure chamber 521 above the chucking plate 506 and the pressurechambers 522, 523 are supplied with pressurized fluids such aspressurized air or atmospheric air or evacuated, via the fluid passages31, 33, 34 to 36 connected to respective pressure chambers.Specifically, the regulators connected to the fluid passages 31, 33, 34to 36 of the pressure chambers 521 to 523 can respectively regulatepressures of the pressurized fluids supplied to respective pressurechambers. Thus, it is possible to independently control the pressures inthe pressure chambers 521 to 523 or independently introduce atmosphericair or vacuum into the pressure chambers 521 to 523. With thisarrangement, the pressures of the pressure chambers 521 to 523 can pressan entire surface of the semiconductor wafer W except a peripheralportion thereof at a uniform force, and pressure of the pressure chamber522 can be controlled independently of pressure of the pressure chamber523. Therefore, it is possible to control a polishing rate at theperipheral portion of the semiconductor wafer W, i.e., a polishingprofile of the peripheral portion of the semiconductor wafer W.Additionally, when a pressing force of the retainer ring 3 iscontrolled, more detailed control can be achieved.

In this case, the pressurized fluid or the atmospheric air supplied tothe pressure chambers 522, 523 may independently be controlled in termsof temperature. With this configuration, it is possible to directlycontrol a temperature of a workpiece such as a semiconductor wafer froma backside of a surface to be polished. Particularly, when each of thepressure chambers is independently controlled in terms of temperature, arate of chemical reaction can be controlled during chemical polishingprocess of CMP.

The chucking plate 506 has suction portions 540 extended downwardlytherefrom between the edge bag 504 and the torque transmitting member507. In the present embodiment, four suction portions 540 are provided.The suction portions 540 have communication holes 540 a communicatingwith a fluid passage 37 comprising tubes and connectors. The suctionportions 540 are connected to the compressed air source 120 via aregulator (not shown) connected to fluid passage 37. The compressed airsource 120 can develop a negative pressure at lower opening ends of thecommunication holes 540 a of the suction portion 540 to attract asemiconductor wafer W to lower ends of the suction portions 540. Thesuction portions 540 have elastic sheets 540 b, such as thin rubbersheets, attached to their lower ends, for thereby elastically contactingand holding the semiconductor wafer W on lower surfaces thereof.

Next, operation of the top ring 1 thus constructed will be described indetail below.

In the polishing apparatus constructed above, when a semiconductor waferW is to be delivered to the polishing apparatus, the top ring 1 as awhole is moved to a position to which the semiconductor wafer W istransferred, and the communication holes 540 a of the suction portions540 are connected via the fluid passage 37 to the compressed air source120. The semiconductor wafer W is attracted under vacuum to lower endsof the suction portions 540 by suction effect of the communication holes540 a. With the semiconductor wafer W attracted to the top ring 1, thetop ring 1 as a whole is moved to a position above the polishing table100 having a polishing surface (polishing pad 101) thereon. An outercircumferential edge of the semiconductor wafer W is held by theretainer ring 3 so that the semiconductor wafer W is not removed fromthe top ring 1.

For polishing the semiconductor wafer W, attraction of semiconductorwafer W by the suction portions 540 is released, and the semiconductorwafer W is held on a lower surface of the top ring 1. Simultaneously,the top ring air cylinder 111 connected to the top ring drive shaft 11is actuated to press the retainer ring 3 fixed to the lower end of thetop ring 1 against the polishing surface on the polishing table 100under a predetermined pressure. In such a state, pressurized fluids arerespectively supplied to the pressure chamber 522 and the pressurechamber 523 under respective pressures, thereby pressing thesemiconductor wafer W against the polishing surface on the polishingtable 100. The polishing liquid supply nozzle 102 supplies a polishingliquid Q onto the polishing pad 101 in advance, so that the polishingliquid Q is held on the polishing pad 101. Thus, the semiconductor waferW is polished by the polishing pad 101 with the polishing liquid Q beingpresent between the (lower) surface, to be polished, of thesemiconductor wafer W and the polishing pad 101.

Local areas of the semiconductor wafer W that are positioned beneath thepressure chamber 522 and the pressure chamber 523 are pressed againstthe polishing surface under the pressures of pressurized fluids suppliedto the pressure chamber 522 and the pressure chamber 523. Therefore, bycontrolling the pressurized fluids supplied to the pressure chamber 522and the pressure chamber 523, polishing pressure applied to thesemiconductor wafer W is adjusted so as to press an entire surface ofthe semiconductor wafer W, except a peripheral portion thereof, againstthe polishing surface at a uniform force. Simultaneously, a polishingrate at the peripheral portion of the semiconductor wafer W can becontrolled to control a polishing profile of the peripheral portion ofthe semiconductor wafer W. Similarly, the regulator R2 regulatespressure of pressurized fluid supplied to pressure chamber 521 to changea pressing force to press the retainer ring 3 against the polishing pad101. In this manner, during polishing, the pressing force to press theretainer ring 3 against the polishing pad 101 and the pressing force topress the semiconductor wafer W against the polishing pad 101 areproperly adjusted to control a polishing profile of the peripheralportion of the semiconductor wafer W in great detail. The semiconductorwafer W located below the pressure chamber 523 has an area to which apressing force is applied via the abutment portion 571 b of the torquetransmitting member 507 by a fluid, and an area to which a pressure ofthe pressurized fluid is directly applied. Pressing forces applied tothese areas have the same pressure.

As described above, the pressing force applied by the top ring aircylinder 111 to press the retainer ring 3 against the polishing pad 101and the pressing forces applied by the pressurized fluids supplied tothe pressure chamber 522 and the pressure chamber 523 to press thesemiconductor wafer W against the polishing pad 101 are appropriatelyadjusted to polish the semiconductor wafer W. When polishing of thesemiconductor wafer W is finished, the semiconductor wafer W isattracted to the lower ends of the suction portions 540 under vacuum. Atthis time, supply of the pressurized fluids into the pressure chamber522 and the pressure chamber 523 is stopped, and the pressure chamber522 and the pressure chamber 523 are vented to the atmosphere.Accordingly, the lower ends of the suction portions 540 are brought intocontact with the semiconductor wafer W. The pressure chamber 521 isvented to an atmosphere or evacuated to develop a negative pressuretherein. This is because if the pressure chamber 521 is maintained at ahigh pressure, then the semiconductor wafer W is strongly pressedagainst the polishing surface only in areas brought into contact withthe suction portions 540.

After attraction of the semiconductor wafer W, the top ring 1 as a wholeis moved to a position to which the semiconductor wafer W is to betransferred, and then a fluid (e.g., compressed air or a mixture ofnitrogen and pure water) is ejected to the semiconductor wafer W via thecommunication holes 540 a of the suction portions 540 to release thesemiconductor wafer W from the top ring 1.

The polishing liquid Q used to polish the semiconductor wafer W tends toflow through the small gap G between the outer circumferential surfaceof the edge bag 504 and the retainer ring 3. If the polishing liquid Qis firmly deposited in the gap G, then the holder ring 505, the chuckingplate 506, and the edge bag 504 are prevented from smoothly movingvertically with respect to the top ring body 2 and the retainer ring 3.To avoid such a drawback, a cleaning liquid (pure water) is suppliedthrough the fluid passage 32 to the cleaning liquid passage 551.Accordingly, the pure water is supplied via a plurality of communicationholes 553 to a region above the gap G, thus cleaning the gap G toprevent the polishing liquid Q from being firmly deposited in the gap G.The pure water should preferably be supplied after a polishedsemiconductor wafer W is released and until a next semiconductor waferto be polished is attracted to the top ring 1.

In the third embodiment described above, the fluid passages 31, 33 to 37are provided as separate passages. However, these fluid passages may becombined with each other, or the pressure chambers may be communicatedwith each other in accordance with a magnitude of a pressing force to beapplied to the semiconductor wafer W and a position to which thepressing force is applied.

In the third embodiment shown in FIGS. 20 through 22, the polishingsurface is constituted by the polishing pad. However, the polishingsurface is not limited to this. The polishing surface may be constitutedby a fixed abrasive, as described in the first embodiment.

As described above, according to the third embodiment of the presentinvention, sufficient torque can be transmitted to the substrate by thetorque transmitting member. Further, an entire surface of a substrateexcept a peripheral portion thereof can be pressed against a polishingsurface at a uniform force by pressure of a second pressure chamber, andpressure of a first pressure chamber can be controlled independently ofthe pressure of the second pressure chamber. Therefore, it is possibleto control a polishing rate at a peripheral portion of semiconductorwafer W, i.e., a polishing profile of the peripheral portion of thesemiconductor wafer W.

INDUSTRIAL APPLICABILITY

The present invention is suitable for use in a substrate holdingapparatus for holding a substrate such as a semiconductor wafer in apolishing apparatus for polishing the substrate to a flat finish, and apolishing apparatus having such a substrate holding apparatus.

1-23. (canceled)
 24. An elastic membrane to be brought into contact witha substrate, said elastic membrane comprising: an abutment portionconfigured to be brought into direct contact with the substrate; a firstannular connecting portion extending upwardly from said abutment portionto form a first wall; and a second annular connecting portion extendingupwardly from said abutment portion to form a second wall, wherein saidfirst annular connecting portion and said second annular connectingportion are concentric with each other, and wherein said second annularconnecting portion is located radially outwardly of said first annularconnecting portion.
 25. The elastic membrane according to claim 24,wherein said elastic membrane is made of an elastic material.
 26. Theelastic membrane according to claim 24, wherein said first annularconnecting portion is thinner than said second annular connectingportion.
 27. The elastic membrane according to claim 24, furthercomprising a portion to be held by an elastic membrane holder.
 28. Theelastic membrane according to claim 24, wherein said abutment portionhas an opening.
 29. An elastic membrane for use in a substrate holdingapparatus for holding a substrate and pressing the substrate against apolishing surface, said elastic membrane comprising: an abutment portionconfigured to be brought into direct or indirect contact with thesubstrate; and a connecting portion extending upwardly from saidabutment portion, said connecting portion having a thin portion which isthinner than said abutment portion.
 30. The elastic membrane accordingto claim 29, wherein said thin portion is formed so as to be constrictedinwardly in cross-section.
 31. The elastic membrane according to claim29, further comprising a portion to be held by an elastic membraneholder.
 32. The elastic membrane according to claim 29, wherein saidabutment portion has an opening.
 33. An elastic membrane for use in asubstrate holding apparatus for holding a substrate and pressing thesubstrate against a polishing surface, the substrate holding apparatusincluding a top ring body having a space formed therein and a verticallymovable member capable of moving vertically in the space of the top ringbody, said elastic membrane comprising: an abutment portion configuredto be brought into direct or indirect contact with the substrate, saidabutment portion being located below the vertically movable member; anda connecting portion extending upwardly from said abutment portion andto be connected to the vertically movable member, said connectingportion having a thin portion which is thinner than said abutmentportion.
 34. The elastic membrane according to claim 33, wherein saidthin portion is formed so as to be constricted inwardly incross-section.
 35. The elastic membrane according to claim 33, furthercomprising a portion to be held by an elastic membrane holder.
 36. Theelastic membrane according to claim 33, wherein said abutment portionhas an opening.
 37. An elastic membrane for use in a substrate holdingapparatus, said elastic membrane comprising: an abutment portionconfigured to be brought into direct or indirect contact with asubstrate, said abutment portion having a flange projecting outwardly;and a connecting portion extending upwardly from a base portion of saidflange, wherein said abutment portion, said flange, and said connectingportion are formed integrally, and wherein said connecting portion ismade of a material that is different from a material of said abutmentportion.
 38. The elastic membrane according to claim 37, wherein saidabutment portion is made of a rubber material, and said connectingportion is made of a material harder than said rubber material.
 39. Theelastic membrane according to claim 37, wherein said abutment portion ismade of ethylene propylene rubber, polyurethane rubber, or siliconerubber.
 40. The elastic membrane according to claim 37, furthercomprising a portion to be held by an elastic membrane holder.
 41. Theelastic membrane according to claim 37, wherein said abutment portionhas an opening.
 42. An elastic membrane for use in a substrate holdingapparatus, said elastic membrane comprising: an abutment portionconfigured to be brought into direct or indirect contact with asubstrate, said abutment portion having a flange projecting outwardly; aconnecting portion extending upwardly from a base portion of saidflange; and a member detachably attached to a lower surface of said baseportion of said flange, wherein said abutment portion, said flange, andsaid connecting portion are formed integrally.
 43. The elastic membraneaccording to claim 42, wherein said member has a lower adhesiveness tothe substrate than an adhesiveness of said abutment portion to thesubstrate.
 44. The elastic membrane according to claim 42, wherein saidabutment portion is made of ethylene propylene rubber, polyurethanerubber, or silicone rubber.
 45. The elastic membrane according to claim42, further comprising a portion to be held by an elastic membraneholder.
 46. The elastic membrane according to claim 42, wherein saidabutment portion has an opening.
 47. An elastic membrane for use in asubstrate holding apparatus, said elastic membrane comprising: anabutment portion configured to be brought into direct or indirectcontact with a substrate, said abutment portion having a flangeprojecting outwardly; a connecting portion extending upwardly from abase portion of said flange; and a hard member embedded in said baseportion of said flange, said hard member being made of a material harderthan material of said abutment portion, said flange, and said connectingportion, wherein said abutment portion, said flange, and said connectingportion are formed integrally.
 48. The elastic membrane according toclaim 47, wherein said abutment portion is made of ethylene propylenerubber, polyurethane rubber, or silicone rubber.
 49. The elasticmembrane according to claim 47, further comprising a portion to be heldby an elastic membrane holder.
 50. The elastic membrane according toclaim 47, wherein said abutment portion has an opening.